I too have used Dulux Duramax clear gloss and White Knight Acrylic over a decal but not vinyl.

I recall ages ago a forum member did a whole vinyl sticker over the whole guitar body. It was a black and white union jack over an SG. not sure what clear coat he used over the sticker, maybe PM him.
heres the link http://www.buildyourownguitar.com.au...ead.php?t=3549