Hmm, I have no experience with Sculpey Glaze. What is it made of, is there any info on the bottle? Acrylic paints usually work on almost any type of surface but I can only guess. I use the same paints for my pony customs as well as clay (polymer clays and Apoxie Sculpt), and I've used them over polyurethane varnish too. I can warmly recommend priming the clay with e.g. gesso prior to painting, it helps the paint to stick better and thus gives you a more even result with less coats. Hope this helps!