The SEM etching primer -- isn't that for metal?
SEM self etching primer #39693 Green was originally made for auto body repair that I have used at work for years.
I also found many years ago that it works better than any other type primers on plastic, cast resin, tin plate, brass, stainless steel, copper, etc.
All brass, plastic and cast resin engines I paint, its the only type primer I ever use.
I also restore old Lionel and Ives tin plate standard gauge train sets using it only as my primer.
Have never had in all my years of painting anything with the paint ever coming off, or even when masking for another color.
All my paint colors are chosen from a auto paint color selector called Dupont SpectraMaster Solid Color Library showing every possible shade of any color.
Each color has a number and I get my buddy at the auto paint store to mix me 4oz of the color I want.
Two type auto paints I use are Nason Ful-Base B/C and Dupont Chroma Premier Basecoat.
Paint reducers are Nason Ful-Base 441-21 and Dupont Basemaker 7175S mid Temp.
For a semi-gloss finish I use PPG Duracryl DCA 468 clear lacquer thinned with #105 lacquer thinner. For a flatter finish I add a flatting agent to the clear.
Using this system I can match any R/R colors as well as when spraying one color I can let it dry for 1/2 hour and I'm ready to tape off for another color.
I have painted, decaled and either semi-gloss or semi-flat finished complete passenger sets as well as many engines finished in one day.
Ernie