If they're track-only tires, it should all come off after several laps at speed. Could it be that you've flat-spotted one or more of those tires, which is the actual source of the vibration?

Yes, a torch and paint scraper will work, but it takes forever. I did it last winter to four hand-me-down tires and I'll never do it again. Took about an hour per tire. However they had not yet been mounted and balanced, so I was worried about getting a good initial balance. Your tires have already been balanced, so you won't have this issue.

I've used those tires at lapping days before and on a heavy car they're pretty awful as far as heat management goes. Mine got slick after 5 summertime laps on a 3200# AWD turbo.

-Cy
1991 Mitsubishi Galant VR4
1999 Spec Miata

dba Speed Shack - Norwood, MA