I have a simple Craftsman compressor 150psi max, their 33 gallon value model--I dont recall the CFM-to PSI rating but I dont think it is enough to really use for extended periods of blasting...will have to double check. I do have this mated up with the 50lb Central Pneumatic Sandblast tank...my compressor works hard to keep up for larger projects...but works well for the small stuff, bead blasting carbs, cases, touching up sections of the frame, etc... I think its fine for what I do, but would like to have a dual stage...something rated much higher in terms of CFM.
I use a #8 glass bead which is pretty gentle medium grit?, set the compressor to around 50 to 60 psi? Not sure if glass beads are the same as Soda Blasting though.
Some other thoughts...make sure you spend the most of your time prepping the piece to be cleaned. Remove any and all soft sludge, caked on garbage, etc; the better you prep your workpiece, the better your finished product will be. I think for my Kawasaki Triple Cases, I have over 40 tedious hours cleaning before blasting them with glass beads...but the finished product probalby looks better than factory.
too much garbage, and you will not have an even surface finish, as the gunky stuff will shield or mask the metal underneath. Blasting should not be used to remove the rough gunky stuff for sure. Hope that helps?
5 to 6CFM seems to be low, as does the volume of the tank, and you can overwork the machine...what you describe is good for low volume stuff like air nailers and the like.
I will try to post some pics later tonight and offer the specifics as far as CFM HP, etc!