plaster walls with rapid set (all the low points) then use your 1800 feather edge from the bottom of the wall and pull it horazontally up the wall, this will shave off all the high points of f your rapid set. It doesnt need to be perfect as long as it is reanonably straight.
I've done a job about 4 months ago and i have saved the pics in members photo section (saved under woody 1) long story.