You can double clutch while upshifting or downshifting.

With cars today there is no point in double clutching unless your synchros have gone bad. That's why you have synchros, so you don't have to double clutch. And there is no point in saving wear on the synchros, since for normal driving and with proper tranny maintenance synchros should last quite a long time.

So, unless you are driving a 1950s packard or studebaker, or you lost a synchro, don't worry about it.