Lube your mag and cycle through a few full mags worth of BB's. Don't release them with your AEG but rather push the little tab on the top of the mag so that they come shooting out. Up to you on how to catch them. I just aim it into an empty bag or box.
I save a little bag of BB's that I use just for lubing mags. probably about 3 mags worth but it save getting excessive amounts of lube on your hopup.