Review on Pebeo Vitrea 160: Enhance Glass Painting with 45 ml Glass Paint Thinner by Nikki Grossarth

My white dots and round shapes are drying with a depression in the middle. I put on two coats and it's still the same. I heated one piece as directed and no change when you heat it. I used brushes of different shapes to apply, the result is the same. The glass I apply this to is a very pure black, as smooth as possible. I need the dotted glass for the monarch butterfly that I am making from stained glass and this will be the outer edge of the butterfly. The dents in the dots are not what I want and now I've done the third coat but the result is the same. Why?!?! Why can't you dry an even shape without a dent?! I hope someone can help with this. I have contacted Pebeo, no response yet.