I use 80 or 100 grit on a belt sander to level them out when they start to get that feathered/ramp look. Doesn't really leave any marks, at least a lot less than are already on them from the track. I only had to do mine once around mid season. I've been happy with the wear on these tires. I ran the same ones all season except I put a new RR on for 4 or 5 races then cut it and went back to the other which won me a race with 19 races on it. I really thought they wouldn't last long (based on my experience prior to legends cars), and I was pretty vocal about that. I was totally wrong. Any added cost due to tire wear is definitely offset by the parts savings due to the fact there are less wrecks and spins are easier to avoid. Also, I've heard that brake fluid works better because you can always claim it was accidentally spilled on them
Wouldn't work here though as our tech guy has been wearing his durometer out on these things to make sure we are all close, since he says the are all soft by the rule book anyway.