I used a 4.5" angle grinder with an abrasive disc with really good results. No tearout, no gouging, no melting. Finished off with screens on the rails & blocks on the flat areas.
The photo is after the grinder but before the hand work.
I have a furniture building background. I tried a planer but thought removing the lines would be a pain. The grinder was just handy. Its no work of art, but it surfs fine. I wasn’t risking very much, the foam cost $7 at Home Depot.
I’m gonna have to try some wood one of these days. Bert, your boards are beautiful.