Acoustic treatment for a garage ceiling

I'm helping a friend convert his garage to a HT. He's going to put up studs, add insulation, and sheetrock the walls (cinder block construction) but he doesn't want to put in a suspended ceiling. He'll run cables in conduit, hang track lighting, etc. and paint the ceiling flat black. His question: Are spray-on acoustic treatments effective? If so, which work best? Can he apply them or must it be done by a contractor?

Any and all advice for taming a highly reflective ceiling will be most appreciated.

Will