Devitrification often occurs on the edges of glass, and can be seen as a thin line of devitrification -often looking like smudges that won't wipe off - where the edge has flattened during the fusing. There are some ways to avoid this.
Avoid grinding if at all possible.
If you must grind, use fine heads/grits. Then clean immediately before any part of the glass dries. You may need to clean part of the glass piece before the grinding is complete to avoid any drying of the powder on the edge of the glass.
Clean well with a minimum of soap and rinse with water that does not have a lot of minerals in it. Polish well with plain paper towels or frequently changed microfiber cloths.
Window cleaning products are not usually appropriate, especially if they contain ammonia.
Avoid introducing oils from the cutter by scoring with a dry cutter or use a specially devised cutting fluid. Cleaning solutions that have additives to be kind to hands or scents should be avoided.
The edges of some glasses devitrify more easily than others. If this continues to be the case after all cleaning efforts have failed, then use a devitrification spray, but continued cleaning is still necessary. There are no short cuts in cleaning.