Got all the doors off the cabinets and set up an "assembly line" in the basement to work on.
Next day, we got to filling the holes from the old hardware with wood-filler and sanding it smooth. We are replacing the handles with knobs so one hole needed to be filled and smooth. Did this on the inside and outside and also filled any knicks or other imperfections in the door. Got them sanded smooth before finishing for the night.
Final part of the preparation stage was washing down the cabinets with TSP and water (about 1:15) and then again with water to remove any film left by TSP.