I think you simplify first where you already are, then downsize to what's working, for the next move. I've had forced moves from the larger to the smaller, and it was painful and not practicable. Now I'm in a house about 4 times the size we now need, and I have simplified to the extent that I think our next move could feasibly be to a condo with indoor pool on the premises, which I need more than I need sleeping space for 20-30 people indoors and an equal number outside in tents (which we only have because we could have it easily after the kids moved out).
For me the simplification includes narrowing the stuff to what we would definitely keep on a move, and what we would leave behind. We have whole rooms of leave-behind stuff which we'll donate to the church on our eventual departure, because they do pick up when it's a houseful being donated. I make sure not to put anything large into those rooms that I would want to take, because I know that when we do move, that approach will make it simpler for the movers-- I can just hang "do not disturb" on those doors.
So by thinking and preparing in advance, I do think it's better done that way.