The engine has a decal on the engineer's side just in front of the cab that, in my case, says "Dange 500 volts". Yes, it was missing the "r". Oops! But, upon further research of prototype photos, it turns out that that text didn't appear until later versions of the NW2, so this engine didn't have that anyway. After not finding anything on the Internet specifically mentioning how to remove S-Helper Service decals, I decided to apply Walthers Solvaset. I would apply it and let it sit for a few minutes, and then use a Q-tip to rub it hard until the Solvaset completely disappeared. This took probably about 5 or 6 attempts before I started seeing some progress. So I continued. Near the end I applied some Solvaset to a small piece of paper towel and then used my finger nail behind it to rub off more of the decal. As you can see, the decal is gone, but some residue remained. My plan is to weather the engine, so this "blotch" will be hidden eventually. None of the paint itself was affected using this method. No guarantees here; just reporting my experience.
I had painted the inside of the wheel faces with Floquil Rail Brown several years ago, so they were done (although they are barely visible). In the photo below, you can see where I have weathered the sideframes of the trucks of the engine. That was done using a small hand brush and Bragdon Enterprises' weathering powder (a dark brown/rust color). And, no, the dust on top of the model is not part of my formal weathering process; I'd been doing some layout construction work recently and forgot to clean the top of the model when I took the photo.
Here's a close-up photo of one of the weathered trucks. More to be done, especially to the journal caps.
One of the things that is noticeable, even in black-and-white photographs, is that the PRR engines' handrails were painted a yellow color. I decided to do that with this engine as well. I am using Floquil's "Reefer Yellow" for this. I used a very thin hand brush to carefully paint the handrails, taking my time as one small slip would put a bright yellow blob on the engine's body. The factory-painted model had yellow at the ends of the footboards and the steps on the pilots. The handrails, the cut-lever, and the handrails to the cab were all painted yellow by me. I followed photographs as published in the Pennsylvania Railroad Diesel Locomotive Pictorial Volume Ten book. Compare this against one of the above photos. One thing I noticed looking at prototype photos is that the handrail on the right-hand side, the one with the inverted "U" shape at its top, doesn't quite match the prototype. On the PRR, that handrail doesn't have the "U" shape, but rather is a just a simple 90-degree bend to the body (i.o.w. the whole "U" section isn't there). I decided that, for now, I'll just let it be. It is easy enough to pop it out later on and form a new one out of brass wire.
Same as the rear of the engine, the front handrails were also painted. The small angled handrail in front of the radiator I believe was painted all the way down to the body (although that is hard to make out in the black-and-white prototype photos). Either way, I didn't want to risk getting yellow paint on the radiator grill, so I only painted the horizontal section of the bar.
Although I only have seen black-and-white photos of the PRR NW2 engines, it seems like the bell did not have the body color. Perhaps it was a brass or gold color. I suspect a painted bell wouldn't ring as clearly as one in its natural state. Since I don't have a brass or gold paint color, I decided to paint mine with Polly Scale "Depot Buff". It was a rather simple project, but did require a very small hand brush and a steady hand.
With all the details added and any last-minute painting done, it is now time to actually weather the body. I didn't want to have any rust showing, because I want this to represent a well-maintained engine. However, it is a work horse, so it needs to look a bit dirty. Dusty, unwashed is what I was looking for. First, I wanted to try a technique I have recently learned about, and that is to highlight edges with a regular pencil (you can see it in the photo). I decided to highlight all hard edges with the pencil. It works really well, but it is extremely subtle. As an example, here I've used the pencil to highlight the edges of the louvers of the air intakes. The ones on the right/bottom have been done, while the ones on the left/top have not.
I used that same technique along the sharp edge of the walkway, the door handles, the door hinges, and the handrail near the top.
Here's a close up of one of the trucks, where I used a pencil to highlight the edges of the sideframes. The journal box on the right shows it rather well in the light. Overall, it is extremely subtle, but I could tell a difference in person between a truck that had been so treated and one that hadn't. The neat thing is that if you don't like, use the eraser to get rid of it.
I then used several colors of the Bragdon Enterprises weathering powders to make the body look dusty. Nearly all surfaces were touched in this process.
On top I did some tiny paint damage when I was trying to experiment with putting a spark arrestor on the stacks. So, I touched up with some paint, which is obviously "wet" and not weathered yet. However, I kind of liked the look. It makes it look like the stacks have been recently worked on and some patching compound has been applied to seal the connection. I can always come back and add weathering powders to it to hide it, but for now I'll leave it.