I drilled two holes at 1'9" from the bottom of the side sill, and then formed the music wire to fit. Music wire is harder to work with, but it maintains its shape better than brass wire as you handle it. So, for the somewhat thicker grab irons, I used that.
For the shorter grab iron above the first one, I drilled two holes at 3'6" from the bottom of the side sill, and spaced them 2'3" apart. I then used the same music wire on the car's end to fit between the vertical styrene parts. The key thing to remember is that the wire must not stick out behind the styrene too far. Since it is next to impossible to cut these after they are installed, you have to kind of guess at their desired depth and trim them to length before gluing in place. For glue I used superglue throughout.
There is a grab iron that goes up some distance of the length of the corner post. It is shown here in the photo, but I didn't quite formed it correctly.
It is 4'3" long. After drilling the holes, I positioned it with two strips of wood to hold it some distance from the car's body and level. When I glue the grab irons in place, I use a small tool I bought at a local train show, which is basically a wooden dowel with a sewing needle stuck in one of its ends. The eye of the needle is cut in half, so that you are left with a pitchfork shape. The glue is suspended in between the pitchfork ends until you touch it to the parts. By holding the tool to the intersection of the grab iron and the styrene hole, the glue flows into the hole and surrounds the wire. This may form a slight bulge, but I think that represents the mounting eyelets that the prototype grab irons have, which are hard to form in scale models (unless the detailing parts are professionally designed and produced).
There is a longer, horizontal, grab iron that is of a thinner diameter, so I used a slightly skinnier brass wire (just under one scale inch) to form it. I drilled two holes, one at 8" in from the car's side, and one at 3'9" in. I put a 90-degree bend in one end of the wire.
Then, using the holes as my guide, I mark and bend the second bend. Ideally you are striving for the brass wire to fit perfectly between the holes you've drilled. Here, you can see that there is a slight bow-out in mine, so the bends in the wire are just a touch too far apart for the holes. If you are a perfectionist, you can go back and try again. On some that are too far off, I will do that. But for some I just let it go. The cars I am modeling, for my modeling time period, are about 40 years old, so they are going to sustain some wear and tear and damage. By not having the time (and perhaps not having yet developed the necessary skills), my slightly "sloppy" work emulates that wear-and-tear. Or at least that is how I rationalize it away in my mind.
The grab iron then requires some additional bends. I grab the wire to just include a bit of the 90-degree bent wire with a pair of flat needle-nose pliers. At first I bent this with my fingernail, but I quickly found out that using a metal file was easier and less painful. I push the file against the short section of the brass wire, until it is at a 90-degree bend to the section that I have in the pliers. You have to grab onto to wire very tightly, otherwise it will just spin in the pliers. The exact same bend needs to be made on the other end. I take a mental picture of how far the pliers are up to the short section, and try to replicate that on the other end.
This is the shape that you are left with when you do the bend with the file.
After bending the other end likewise, I trim the excess material off.
Now comes the hard part. We need to make a very short Z-shape bend into the short part of the grab iron. I put the short end length-wise into the flat needle-nose pliers, and then start to put a 90-degree bend into it. Since this is such a tight bend, it is hard to do, and it might damage the remainder of the grab iron. I carefully get it started with my other hand (fingers are easier to manipulate than tools!), and finalize the bend by pressing hard with the end of the metal file, pushing against the pair of pliers. Quite a bit of force is needed.
This shows the final shape of this Z bend. Of course, the trick is to get both ends to come out looking the same, which was not the case for the subject in this photo.
It is then just a matter of gluing the grab iron into the body up to the tight Z-bend. I then tried to trim the excess material as best I could from inside the body. This completes the one-of-a-kind grab irons. The thing to note here is that I have shown only one set of these grab irons. The diagonally-opposite corner of the car needs to get those exact same grab irons. I did one grab iron at a time, and then replicated that for each corner for all three of the cars I am building. This makes it go easier as you develop a routine for drilling the holes and forming the grab iron.
Now, we are going to get started on the "ladder" like grab irons on the other corner of the car. On the ends of the car, a new piece of vertical bar needs to be added to the body to support those grab irons. Looking at the prototype photo I used a scale 2"x3" strip of styrene (the 3-inch width is the face of the piece, while the 2" is the depth of the piece), and filed the top part down to about a scale 1" thickness.
That filed-down area is then laid on to the hopper body, while a small clamp holds the other end in position against the backside of the end sill. I bought these plastic clothespins years ago and I don't remember where. They exert very little pressure, so they are great for delicate parts, such as these. Of course, them being plastic, you have to watch out for where you apply the styrene glue. I am going to use Tichy's 18-inch drop grab irons (highly recommended!), so the styrene part is glued such that its center is located 18 scale inches away from the center of the corner posts.
With the glue thoroughly dry, I drilled the holes for those grab irons. There are three such drop grab irons on the ends of the car, and there is a fourth one just below the top-chord, but that is more of a drooping straight grab iron. I spaced the grab irons 1'6" apart.
Again, to avoid them sticking out too far in the back, I trimmed the ends of the Tichy grab irons just enough to go through the styrene before gluing them in place. The one at the top I cut even tighter, and then used the pair of flat pliers to somewhat straighten out the bend in the grab irons. This makes it droop down a bit, as is seen in the prototype photos.
After adding those to the opposite ends of all the cars, I needed to do a similar thing to the sides of the cars, at the same corners. Again, an extra piece of styrene needs to be installed. This time, it appears that it is a flat bar which has end splice plates applied. So, I cut the 2"x3" styrene parts to rough length, and then filed one end down to match the slope of the hopper. I marked a center line, 18" from the center of the corner post's center, and then glued the styrene strip in place (which is a bit of a challenge until the glue "grips").
I cut two 1-foot 1"x3" splice plates and glued those over the joints. Next, I marked the locations of the holes. Again, there is a drooping grab iron just below the top-chord. On the sides there are five drop grab irons, with the bottom one placed just above the top of the side sill. The top four grab irons need to line up with the ones already installed on the ends.
It was then just a matter of drilling the holes and attaching the grab irons as before. If you drilled the holes' locations accurately, the Tichy grab irons just drop in. There are a total of 18 parts per car end that need to be added to do the grab irons (36 per car, or 108 pieces total for the three cars I am building). This completes the grab irons section, but there are more details to add to the lower part of the car, including a few more wires.