I don't mean the obvious ones, such as Mr Super Clear varnish (if you can get it) or big-person spot-cream containing benzoyl peroxide (for stain-removal on vinyl), although they're great as well: which more unusual products do you find useful for customising dolls?
I like, and get through a lot of, Dylon fabric-paint pens – for dyeing doll-clothes (usually darker!). However, I can't find Dylon any more and am going to try new brands that I found on Amazon. Ideal for covering some of Monster High's more 'heavily patterned' new clothes-materials.
Winsor & Newton artists' varnishes are the only ones I've found so far (at least easily available in the U.K.) that will work on soft plastics – everything else just stays sticky.
DecoArt Metallics acrylic paints are excellent: I use them on everything, even dolls' heads. Great consistency and rich colours!
Are there any other products you can recommend? :)