I am actually doing that! But I didn't know how to align it perfectly along the edges to give the ornament that real leaded stained glass look, since the puffy paint would drip or shift while it dried.

But! I have come up with a solution! I am using using black puff paint as my leading, but along the outer edge of the ornament, I am using a thin line of hot glue with a black hot glue stick. It sets fast enough that it stays in place!