You need to start by protecting the painted area with painters tape. Take your time and use a straight edge where possible and an exacto blade to get close to the black borders. Once this has been achieved sand the area with 150 grit sandpaper around small pieces of flat wood And smooth the area. Work up to 400 grit gradually.
You may never improve the original yellowing of the wood too much but you will smooth out the planking. You may need to change the painters tape after some time but that’s part of the job. Be patient and you will be rewarded with satisfying results. Finish with a clear shellac coat.
The flippers appear to have imparted no wear so that is good.
The next step is to lightly clear the area to protect this part of your restoration before tackling the painted areas.
If there was flipper wear now is the time to drop some clear on the area to fill the depression and sand the clear smooth. You can make the flipper wear completely disappear if the shellac coat was close.
