Vinyl dye is not a gloss finish and there isn't anything I know of to make it so. Why not use gloss spray paint and protective clear coats? It's far more time consuming, but the results are tremendously satisfying. I modded a case some time back and wanted the monitor to match the color scheme of the case - well, I wanted everything to match - and I used some custom mixed automotive spray (a metallic) and a rattle can satin black and then added some chrome accents with chrome sheeting and pin-striping. Turned out pretty nice:

Grump