Personally, I dont recommend using campden/sorbate to stop/stabilize cider, because it leaves a noticeable chemical taste. But it does work. Rack to secondary to get it off the lees, add half the wine dosage of campden first, make sure it is mixed well in the cider and let it sit for a couple of hours. Then add the regular dose of sorbate.
Or, since you are kegging, if you are using an ale or wheat yeast you can cold crash it to get the yeast out of solution. That is a little more work but the taste is worth it IMHO