Looks like some of our regular members have you pretty well covered here, Nelson. We agree with skipping the Dawn wash altogether; you don't really need to strip the old wax before applying anything new, and if you're waxing every several months then odds are there isn't a whole lot of the earlier application left anyway. Wash and dry the car, clay if needed, use ScratchX 2.0 or Ultimate Polish to clean up any isolated defects, and then apply your wax. If you do have to clay and/or use one of those light cleaners then either process will remove what's left of a previous wax application anyway, so that's just more reason to skip the Dawn wash.