I’ve been using the GW snow effects, to be honest it’s not amazing, it looks good but yellows, so another layer is needed, at first I thought it was a reaction to the glue or paint I had based it on but not so sure now as I’ve tried it over white painted bases too and stuff that’s been painted for a few years , it looks good once white though, but as I say a couple of layers are needed and it’s not cheap either