Besides sandblasting, how can I remove devit?
If your glass is flat, you can sift a very thin layer of Clear powder (about 2 grains thick) over the entire piece and fire it to 1425°F (774°C) - 1450°F (788°C) for about ten minutes, depending on your kiln. This should remove the visible presence of devitrification. Please note: This method only works if you don't intend to fire the piece again, as refiring could restart the crystallization.
For more details on this process, see Quick Tip: Use Bullseye Clear Powder to Fix Surface Flaws.