It's just practice...... I spray down the back of the arms when I'm doing back, then side of arms when they are side on, then arm in air and spray down through wrist, underarm,side of body down to knickerline. Then I get them to keep arm in air whilst I do other side so that u don't get an armpit line. Then I spray front of arms when doing front of body and by that time most of arm is covered anyway. Then just get them to turn wrists up to check all covered. Sorry if that all sounds a bit confusing! Lol I also don't really spray hands and give wrists a quick buff over with bit of couch roll as personally I think the hands are always a tan give away and I hate them looking orange!! X