The metal work is looking quite good.
For the white and yellow paint, you want to make those areas a little more shiny than the other painted parts on the P and S maps. That will focus the washed out part to a smaller area. I use RGB 66/66/66 for white on the P ans S maps.
Also you need to use a fairly dark color for each on the diffuse map - especially the white. On my recent Pacific P-39's and P-40's, I've been using RGB 166/166/163 for white and RGB 191/148/16 for yellow.