I carbonate slightly with CO2 first, as do most people I think. It just goes faster. But carb to a VERY low amount. When dispensed at nitro pressure through a restrictor disk, if you carbed it too much with CO2 you're gonna get way too much foam. The best thing to do is to carb with CO2 to lower than whats needed, then put it on the beergas at dispensing pressure and within a week it will be carbed perfectly.
I'm too lazy and have too many beers going to keep updating this!