Yesterday ended up being hotter than originally forecasted, so I brought the taillight harness inside to work on cleaning/restoring it. I tried using all-purpose cleaner/degreaser to clean the wire loom, plugs and wires. This did not work the best, so I ended up using Gojo Fast Wipes. They seem to cut through the grease and dirt much quicker.
I started by removing the section of loom to the right of the large plug you see on the left side in the picture below. I cleaned the loom in the bathtub so I could spray it with water and cleaner. This loom, other than having overspray on it, is in really good shape. I plan to reuse it. I do not foresee this being true with the other wiring looms on the harnesses I am going to be cleaning and restoring.