It's been 15 years since I used a vinyl paint. Here is what I remember:
1) Cannot put vinyl over any other paint (See 2) below)
2) It uses very agressive (and special) solvents - beware your hands.
3) It definitely builds up. I let it build until I had adhesion problems then had a major sanding job. Sanding is the only way (other than sand-blasting) I remember to get it off.
4) It did not do a very good job on anti-fouling (I live on the NE Atlantic coast)
5) Only advantage is that it was a very hard racing finish.
I think most hard finishes these days are the modified epoxy type.