I used to do this a lot before I got married and now only do so when I am away and sleeping on my own (hotels, etc.). My "technique" is pretty simple, really... I wear loose boxers to sleep in and if I wake up in the middle of the night with a stiffie that won't go away, I grab one of the spare pillows and shove it high up between my legs - with my hardon pointing UP. Well it may seem a bit juvenile but humping the pillow feels great! In no time the friction of the soft pillow and my boxers against my thrusting hips results in my shooting a nice, warm load into my boxers. I fall asleep almost immediately after and it's a real "dead" sleep - though waking up with a sticky mess bewteen my legs is a bit annoying... but worth it!
Tony :wink: