I use a stone to carb all our beers and sodas. Make sure the tank and beer is COLD! I always try to shoot for 30-31F before I start carbonating. Bring the tank to pressure (I use 15-20psi), begin bubbling CO2, crack open the CIP arm with a blow-off hose attached terminating in a bucket of sanitizer. The goal is to hold the tank at pressure equilibrium (gas in the bottom equals gas out of the top via CIP arm) while the carbonation takes place. I can get a 10bbl tank of flat beer to 3.0 volumes of CO2 in about 6-8 hours with this technique. May not be the best one but this is how I do it.
p.s. clean your stones between uses. That just generally good advice throughout life!
Glacier Brewing Company
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