Scratchbuilding is fun and quite a challenge, take for example the fork truck, none are commercially available in O gauge so I made my own .....
https://christopherrussell1.blogspot.com/2019/12/fork-truck-project.html
https://christopherrussell1.blogspot.com/2019/12/fork-truck-project.html
Now the trick is to use very sparingly a light coat of Nitromors, as soon as it begins to bubble and flake wash it off in warm soapy water GENTLY !!, allow to dry overnight, then repeat the process until you are happy leaving the already affected areas intact.
I finished off with a light coat of grey as was used on these old Toads, white paint and lettering was then applied, then to finish off weathered lightly all over the brake van with an airbrush.




Class P3 J27 , using a matt black finish enabled me to use variuos shades of weathering powder that "stains" into the black paint. The white runs in front of the cab are thin white paint apllied with a tiny brush to represent limescale.
Below:- The "toad" brake van
Getting on for twenty years old this model has been painted umpteen times.
I'm rather proud of this accident with Nitromors ! The plastic started melting so I had to wash it off QUICKLY . The resultant layers of paint revealed look quite good with a flaky paint effect. Sometimes you learn from mistakes you make and put them to good use.