You'll probably get some ideas here, but I'd try www.johnbridge.com I think you'll get more ideas faster. Trying to flatten the wall is possible, but may not be necessary, except to make it easier to set the tile evenly. You could probably chip it off, but it may take out chunks. Somebody over there has probably done this and will have some ideas. Unlike floor tile where it should have 100% coverage, that isn't as important (still desireable) on a wall. My unprofessional opinion.