One advice I can give you for the upstroke strumming is to lead the movement with your wrist and let the hand drag a little behind.

As you go up your wrist should bend a little so that it is a little higher than your pick. Also keep you wrist close to the body of the guitar when going up so that as you hit the first strings, you don`t end up having your wirst go away from the guitar but towards it.

Naturally this is the way I do it, some people may do it differently but try it out to see if this helps you.