You should try a ceramic coating - you can do it yourself (it sprays or brushes on) and withstands 2000F. There are several places that sell a variety of colors (cast iron, black, flat, white, chrome, blue, etc.). Although I have yet to use this - I plan to. Here is a place I found where you can buy the supplies: Columbia Coatings

Just go to the Ceramic section. I am sure there are other places out there that sell this stuff.

You may have an issue with your glass beading - might not give sufficient "bite" for the paint to adhere too.