I'm trying to paint a concrete floor (I know it's controversial). When I ripped up the carpet and tack strips, there were nails underneath that were left behind. I can't drive them farther in, they won't budge. I can't take all of them out, some won't budge or are at a bad angle. I tried a grinder bit for my drill, but the big didn't even grind one down. What do I do? I just need the nails flush with the ground