If the goal is to get it out of my system like you describe, I don't do anything I'd describe as prep, rather I set it up like a special occasion. "Writing time" then becomes mixed up with some kind of lil treat, to separate my satisfaction with the writing done from the time spent. This way, even if the writing itself fell flat and I'm disappointed, maybe I still had a a nice time.
Since writing is often a matter of habit once the initial enthusiasm wears off (for longer stuff at least, not like poetry), my best success came from writing being the gravitic center of my day. It needed to be easy to start, and hard to quit early.
I love the west wing I want to live in the west wing I want to bust in (on?) the west wing god I love level-headed discourse it makes my nipples want to stand up and put some dumb fucking COLLEGE STUDENT with BLONDE HAIR in her place with a self-assured monologue FUCK