We recently had a pretty good thread on this topic. Searching might be able to find it.

I have access (well, it's my job) to a full professional setup (walk in 1 car garage size, space suit etc etc) and various other smaller setups, with grits ranging from 20 (tiny pebbles practically) to 250 (basically powder), I've used 36 and 54 grit on prints and have had decent results with them, but I'd want something in the 75 range to smooth them out pretty well, at something like 20-30 psi.

If I was set on painting a print, I'd smooth it with acetone first, then blast it to roughen up the surface. Otherwise, without the acetone, you'd be left with the layers and small gaps.

The other thread has a bunch of good links to home blasting setups.

As for saving money, I've been thinking about making my own for use at home, welding up a decent sized glove box using 1/8" Titanium plate (another thing I have practically unlimited access too, Steel or Aluminum, not so much), good sheet of lexan for a window (using thin clear plastic sheet for a disposable shield, don't want to ruin the lexan, and it'll go quicker than you think). I'd get a commercially available hopper and air supply, but I figure one could easily fashion a reclaimer/separator out of a funnel, some buckets, and a shop vac. The reclaimer would keep the grit to a standardish size, while getting rid of the dust.