This got me to thinking - would spraying the fresh gel coat with something like silicone grease or hair spray or something work to seal it? I imagine a thin film of something like that would be easier to clean off than the sticky gel coat, and would also leave all the gel coat there to be sanded. In some spots where I'd applied it a bit too thin, the acetone ends up taking it all off, leaving spots that need to be refilled. Also it would be a lot quicker and easier to just spray over it than trying to smooth plastic over.