start by trying to firmly rest your forearm on the contoured curve of the guitar. one thing about "technique" that i've always held in mind is: do what's comfortable. techniques are major guidelines that have been found through years and years of people playing but at the end of the day they're still guidelines... not the law of playing guitar. try resting your forearm on the guitar. this will give you a reference point for your wrist and arm to pivot off of while you're strumming. without this point of reference especially when playing off handed, you can get inconsistant movements... it's hard to make progress without conistency.