like its been said cfm is the biggest problem when i left school i done shotblasting for 3 years,we had 2 600cfm compressors to work 2 blast pots and various airless spray equipment like its been said the small ones are good but take a while depending on what medium your going to use sand,chilled iron,j blast,etc we used glass bead on alloy which gave a nice finish where chilled iron would tear it to pieces and dust extraction is a must our blast bay was 60x15 and with no extraction on after 30 seconds you couldnt see your hand in front of your face,chris.