This is just one time Jr has talked about it. He's discussed it many times on his podcast. RC has talked about it as well.
https://twitter.com/DaleJr/status/1290731266183245828?t=zyXWEeVJ2d4cha_xLQCc8Q&s=19
I (Millersport Customs) currently offer over 150 different Nascar decal sheets as well as 3d resin printed products. I'm slowly pulling my stuff from Shapeways to add to here. Some factory stock decals could be added soon.
https://www.printitdecals.com/collections/racecar-decals-millersport-customs
Some time back someone posted about using superglue and possibly micro balloons for creating rust areas under paint. I cannot find that anywhere now. Anyone have any ideas?