I did wonder that, but the white marks were there while I was still scraping, before brushing/scotch pad.
White marks will be there from excess wax. Scotchbrite will polish it out. Reward your board now. Don't bother cleaning it because between the waxing and scraping the. Brass brushing, your base is clean right now. Apply the wax, let it cool, scrape, then scotchbrite. You're done unless you're gonna ride powder. You can nylon after or skip to the cork.
Any cork will work. I've been using a cork top for one of my jars. I've even used a wine bottle cork before lol.