@Mike Yevin Hey! I really appreciate your following and for the valuable input. Currently I am working on some old assets that I had started for this project a while back. I had started working on the original block out and I will post some images of it later this week. Currently I am just finishing the few assets I had started then gauging the scene block out model to see what I need to construct next. I am still trying to figure out the direction I want to go with the destruction the building has sustained.
Ok with this I decided on my colors I wanted to use and then after painting the base textures I found a rust texture online on a seam and then selected the painted areas that were not the right color and brought it into Photoshop and used Match color
Go to Image > Adjustments > Match Color.
Then make the target your original color so it matches that color.
Here is a website for a walk-through tutorial on Photoshop Color Matching
Then after matching the yellow color I cut pieces of the rust and fit them onto the seams where I thought they seemed fit. I am still working on the texture overall but I hope that helps.
As for your other question. As of right now this shot is rendered out from the Marmoset Engine with some prepossessing effects added. I am going to move all the assets I am creating into UDK this week.