I'd go straight water, skip the abrasive. Like This Type Unit
I don't know what your pollution regulations now are, but these are the best way when you have to dispose of the blasted off waste as hazardous waste, then you don't want any sand since you pay for disposal by weight. With straight water (and these systems get white metal from crap) you work over a collection/retention/settling pond, you filter off the water and dry off the waste and load it out only paying disposal for the minimum you can. Regardless that though, for yard efficiency you eliminate so much clean up and masking time over abrasive blasting. When the boat is dry, it's ready for the next step all nice and clean.