I have never used one, but my guess is using the blind squonking technique. In fact...it may have been developed for the 801 and 901 users. This is achieved by pressing gently on the bottle while drawing on the drip tip (not firing the atty). Then when you hear a gurgle or feel the pressure change, stop then take a normal drag (this time firing the atty). On the smaller atties that I use (510s & 306s), I just do a sharp quick drag while pressing the bottle and I'm done. Just a split seconds worth. Don't know how it would need to go with the 901s. You'll get more answers by the 901 Masters shortly, I'm sure.