I don't add any priming sugar to my kegs. The way I see it, you have a CO2 tank so use it to carbonate (two week set and forget is damned easy and reliable) and then serve. Using priming sugar to carbknate also means you'll also need to shorten the dip tube so that you don't get the trub you generated. IMO not worth the hassle. Besides with carbonating via gas you can dial it in pretty exact. Much more so than when adding sugar.