Ive found it best to be laying on my side, when doing it myself
but its better draped over something like the edge of a couch, when its done to you
being on all fours is one thing, but you relax more when your laying on something, and that can cut down on time. being on all fours can end up painful to the knees depending on the surface, so that can tense you up and not only extend the time, but limit the release
another way to speed time up is to be aroused personally, whether you watch porn or teasing, before milking
I wouldnt use a tens unit myself, but shocks are a no go for me
for myself I have a rechargeable massager with a remote and different speeds, and has a cock ring attached that stretches, so you can wear a cage at the same time
with someone else, Ive found a hand is best. a finger inside with the thumb rubbing the outside in the same spot. that is if you want to have some pleasure