Best thing to do to your blasting cabinet.

A Thien baffle dust collector made from a five gallon bucket will save your shop vac. Search Thien Baffle or here is one example. http://www.jpthien.com/smf/index.php?topic=1028.0 Hobby Lobby has some rolls of clear plastic sheeeting and a roll of double stick tape to make new protective film for the glass.