Do not use too much quickset, it is a pain in the ass to sand, you never want to have to sand it. I'm not a professional by any means but i only use quickset to tape and fill large gaps, wait an hour, scrape any high spots with your knife, then do one or two coats with slightly thinned mud. Buy it in the 4 gallon buckets an home depot. Light sanding after and your good to go.

Also a lot of the other guys have some very good tips, a wet sponge, you can buy regular sponges in a two pack at HD, completely removes the need to deal with sanding and all the dust that comes with it, as long as your mud is pretty flat.