I did a wash using Tamiya acrylic XF-1 flat black ( the one I use for scale airplane modeling ) diluted at the ratio of 1 part paint to 16 parts isopropyl alcoohol. I used my track cleaning car for the attempt because the track cleaning car is not permanently on the layout so if the attempt fails no one but me will know about it. I purchased the Jeff Wilson's book " Basic painting and weathewring for models railroaders ". ( Kalmbach books ) It's a good reference book. I didn't want to overdo the wash so I applied it once.