I have over 30 years' experience refinishing nothing but acoustical ceilings, and I now offer a comprehensive training package to painting contractors, at
There are VERY few conventional flat paints that look good on an acoustical ceiling, as most tiles are porous and absorb the paint unevenly. This typicallly leaves streaking on the ceiling, which may not be obvious initially, but when any outside light (or reflected light) hits it at an angle, you're going to be getting a callback from an unhappy customer.
ProCoat is generally available from SW stores, but you have to order it and pay shipping. The advantage to it is that it dries totally flat, and covers well. Always cross-hatch to ensure even coverage.
If you'd like more info about our training package, take a look at our web site and either call or email me.