How do I remove oil base exterior paint from brick?

You need to use a gel type stripper, they make some specifically for stripping brick. Don't sandblast or powerwash it. A lot of times brick is painted to cover up something, like a remodel that didn't match. Read this article before you do it, it will answer your question and more.

Brick Houses - Oldhouseweb.com (http://www.oldhouseweb.com/stories/Detailed/14298.shtml)