I love to paint and glitter is sort of a passion for me. I use the usual Garmar or Damar applied with an airbrush which usually does the trick for loose glitter. If the glitter is just really in there sticking to the paint I just brush it on like normal. If I recall correctly Andy Warhol used this technique relatively often. If you Google a bit you should be able to find his process as well. They make a sealer for glitter which I have never tried. It is usually in the same aisle as the glitter. I know since I was shopping with a friend and she picked some up. She used it on a project involving shoes and it has held up very well. I am not sure if it is archival, nor if it won’t yellow.