I would love to be your buddy, EraserGirl. What sort of workshop is it and do you work at home full-time? also, where will the items from your workshop go once they're out of the room? Just trying to picture this all in my head.
With big projects, I take one of two approaches: (1) break it down into small tasks and then schedule each task or (2) just dive in starting with one corner of the room and working around clockwise (or counter-clockwise, whichever makes sense). I don't think that either is better than the other, it just depends on whether I want to take a more measured approach or if I just want to dive in because I have the motivation at that moment.
I'm not even at the stage of true decluttering. I'm starting by making all the rooms navigable. I'm down to two rooms that are still disasters--the kitchen and my office. The kitchen is an on-going two steps forward, one step back. My office just has way too much stuff in it and I have two children who love to strew everything all around.