[jclark003]

I cut a small slit in center of divit with razor, then used an iron and wet rag to swell up the wood. Takes a while and the rag needs to be flipped and keep wet.

No need to sand down to bare wood. A light scuff should be enough to provide a mechanical bond for new urethane. If the scratches are into the wood you may need a fine/220 grit paper. If you do sand down to bare wood be advised that those sections will be a little lighter for a season or two.