You could get a piece of laminate (Arborite, etc.) and use double sided tape to temporarily attach to the side of the cabinet for a scuff guard. Mark the top with tape or whatever. Combination or adjustable square makes a nice scribe. Hit it with a beltsander and a 40-60 grit belt. Sneak up on the line with finer grits, finish with 120 ish. Remove laminate. As said, take your time and be patient, let the machine do the work.If you have a sander with a vacuum attachment, great. Might be able to hold the vac hose close to the sander.