02/22/24 - I found a location on the layout where I wanted to install a couple of truss bridges. I picked up an Atlas Pratt truss bridge at York last October and I ordered a 24" Menard's truss bridge as well. My plan was to install Gargrave's track on the bridges and realistically weather them prior to installation. This was the location I chose.
Once the Atlas track was removed from the Atlas bridge, I painted both bridges flat black. The next step was to determine how I was going to weather these structures. My original plan was to use hairspray and weathering powders like Joey Ricard did in one of his videos, but I was concerned I would not be able to get into all the tight corners and inside the structural members of the bridge.
Searching the web I came across a product called Metal Effects by Modern Masters. It is a paint that contains iron particles. Once the paint is dry it is sprayed with an activator that actually creates real rust. Can't get more realistic than that! 
This was a fun product to use. And it allows you to create rust on anything.
The bridges were brush painted with two coats of the iron paint and left to dry overnight. The paint is grayish in color. I also varied the thickness in places so the overall effect would not be uniform. This is what the bridges looked like after the paint application.
The next day the bridges were sprayed with the activator from a spray bottle. I sprayed two light coats. Once it dried I did go back and spray some more in places that I felt needed more rust. This is what one of the bridges looked like about a half hour after the activator was applied.
And this is how they looked about two hours later. They do appear a little more orange in these photos than they actually were. This was because I forgot I had the camera HDR setting on.
The larger bridge did seem to rust up more than the smaller bridge. I don't know if this was because one was plastic and the other made of wood, or if my paint applications/thicknesses were different. I was able to make them more uniform with the application of the sealer. The sealer is used to stop the rust process, otherwise the object could keep rusting over time. It probably wasn't necessary for this application since the bridges are not made of metal. The sealer also keeps any of the rust from rubbing off. Here they are after the were sealed and the camera HDR setting turned off.
I then installed the track to both bridges with screws installed from underneath.
Next came out the sawsall and I cut out the bench work where the bridges would go. Some new braces and supports would be installed.
I got some bridge abutments from Scenic Express and bridge shoes from Scale City Designs. These items were painted and weathered accordingly. Once the bridge abutments were installed at the correct levels the bridges were mounted in place. Here is the end result.
I'm really happy how these turned out. I still want to install track guard rails on the bridges. I also need to hook up the lights on the Menard's bridge. Here are some close ups of the bridge details.
