just my 2 cents
i have a 60 gallon compressor and a small 40 gallon blaster
i run teh blaster at about 95 psi (compressor can handle up to 250)
at that psi my cfms i think are around 15-20 or 20-25, somthing like that
regardless, every so often i have to let my compressor sort of catch up, its not all the time, usually only when im doing a large section and constantly running the blaster at full tilt.
the setup was sort of pricey, but i think its worth it, mainly i go over large flat areas with a 7 disk sander with some 80 grit, i just be gentle with it so i dont ruin anything, then i hit it with my DA with some 80 grit, sort of go over the whole thing once more with the blaster mainly because the surface the blaster give the metal gets great adhesion.
otherwise, i mainly just use the blaster for those nooks and crannies, or areas where i just dont want to fuss with any sander.
i like the investment, and if you take the time to do it right, it can definetally pay off.