Anything 3rd party in forza breaks tos and IS a bannable offense.
Most painters use something called glass2k and trace the paint that way. Since all it does is make tabs transparent its an allowed tool for the job. More info here as well as other commonly used painting tricks: Forza Documentation [History, Guides, and More] - #5 by Oliver0023
If you have any questions in regards to this i would be happy to try and help you