I want to parge my exterior walls. However, the previous owners painted the concrete blocks with numerous layers of paint. Unfortunately, nothing I do will fully take the paint off. Do I have to remove the paint before parging and if so any ideas on how to get rid of the paint.

You might want to read this just to help brush up on your technique. Parge the ugly out of your concrete wall by Bill Leonard Issue #57 (http://www.backwoodshome.com/articles/leonard57.html) If you have used paint remover and a pressure washer the remaining paint is well adhered and you can parge over it. Wire brush it well and rub the wall with a small piece of broken concrete block or a very coarse sand paper on a block of wood. Rinse this dust off and then parge, or parjay.

Look at this product http://www.larsenproducts.com/weldcrete.htm

Expect to pay about $40/gal