Question to the paint species

moin moin das schwarz meiner ofens sollt soft. i wanted to give my softail a scissage fly green in metalflake. since i can do quite well with gun painting, i save myself the money for the laugher. of course it will not be the best, but to me that is enough. ask: my paint is of course sealed with clear varnish. is it enough if i only grind it fine and then paint it, or do I still have to prime the better adhesion? oldschoolbob