I use rubbing alcohol (takes moisture off too) use lint free towel and I also wear a pair of lint-free gloves, when assembling the final project, so the oil and finger prints will not get on any glass…some may think this is crazy, but one finger print can leave a mark on the final project.
you can get lint free gloves on Amazon.com
from eHow: Clean and then reclean any glass that is going into your kiln. Specs of dirt, dust from grinding, oil from your skin; all of these can cause nucleation points where devit will have a tendency to occur. Cleanliness is probably the one characteristic that the artist has most control over. I soak the cut or ground glass as soon as I have a piece ready for the assembly stage. This soaking allows the edges of the piece to be cleaned easier and more thoroughly..
Hope this helps