I to was just thinking about bead blasting also alanrockwood. We have one at work with fine silica powder. Most times when blasting metal from a distance of 2½"-70mm. I think with glass it would have to be farther back to get an even spread. Plus you will need to factor in the nozzle of the blaster. Grinding by hand with a paste will give lots more control of the finish product. So I believe hand grinding will be better.