I fill four kegs at a time, prime two or three and force what is left. This way I don't need all of them refrigerated. I used to use about 1/2 the normal amount of sugar and found it to not be enough. Now I use NBs priming calculator and go pretty close but err on the light side.
One I have on draft now is just a little over carbed but not enough to worry about it. After the first pour the next one (two, three...) have a nice head.
It's all about tweaking it to your likes and system.
BTW I serve at about 10lbs.