I'm chiming in only because I'm the one who suggested you try these paints out! But, my answer to you is... I dunno!
Your granddaughter is gorgeous!
Believe me, I'll take all the chiming I can get! I'm no artist, and have no experience or background in this stuff. I have a little art airsprayer that I'm going to try. I cut out more glass and will try spraying skin on both pieces, one set that already has outlines, then skin, then shadow, then touch up detail, and the other like a canvas, skin, then shadow, then detail, and see what works the best. The worst that can happen is that itll all be awful and I throw it away. I do know that there is a real difference in how it looks flat on a table, and up to a window in the sun.
And yeah..she's a cutie! This photo was when she was about 5...she's 10 now.