On one of the two bridges on the layout I wanted to build a walkway across the creek. When I glued the ties down on the bridge, I had accounted for that by placing extended ties every-so-many regular ties. I started this walkway project by cutting and fitting some scale 3" x 12" lumber to form the curved walkway (the bridge track is curved). Once I had the final arrangement, I carefully removed each one and kept them in order. I then used Elmer's wood glue to glue each of them down to the tops of the ties.
Next I cut some scale 4"x4" poles and superglued them to the sides of the extended ties. These poles were about a scale three and a half feet long. I had to use superglue, because the wood glue wouldn't hold them long enough and I didn't think I could get a small clamp on there.
Some of the poles weren't perfectly straight, and because of the curvature of the bridge ties, they weren't evenly spaced. I decided, therefore, to measure and cut individual scale 2"x4" boards to fit on top of the poles. I left about half of the top of the pole exposed for the next board. I used wood glue to glue them in place.
Next, I took a full strip of scale 2"x4" and superglued it to the back of the poles as the second horizontal railing. Since the individual joints wouldn't be visible, I decided to just use a single board. A prototype photo I was following showed the board being attached to the inside, i.e. walkway, side of the poles, but this part of my layout's track has a very tight curve, so I needed the extra clearance for railroad cars' overhang. The way I installed this board was by using some small modeler's clamps to the get board in place and parallel to the walkway deck. I then superglued each joint.
I stained the railing boards the same way I stained the walkway boards with Minwax' "Special Walnut". I also applied some India ink and alcohol mixture. In the background, on the right, if you look closely enough, you can see a person taking a lunch break while enjoying the relaxing flow of the creek below.