Conventional "gelcoat" material only sets up and cures in the absence of air. Making it great to apply inside a female mold before frp is laid over it, but impossible to spray like paint, since you'd have to cover it to cure it. There are supposed to be new "gelcoat" materials that will cure in air but at that point maybe price is a problem?
The gelcoat I referred to is not air inhibited and it didn't cost any more than regular gelcoat. It is handled and sprayed just like usual - thinned with acetone etc. You can even use those disposable Preval sprayers for touch up purposes.
I think the problem with it is what has been said in this thread - most people think it's only good when sprayed into a mould before laminating, otherwise it's too much work.
2 part polys have attained the image of being the only way to go and it has become conventional wisdom as a result.
That isn't true.