We're doing a mix of homechooling/unschooling, but Math is one subject that we actually study.. mostly on the Internet, on Khan Academy, because my son gets bored easily with Math books. Khan is useful as they have videos explaining stuff, which is great as sometimes I don't remember what you're supposed to do with fractions and things like that. When there is something he doesn't quite understand, I try to create new problems and walk him through them until he gets it. My main focus is to keep things relaxed and funny, so there's no pressure. We make jokes, funny drawings of the problems and laugh a lot.
Another thing, I avoid going into teacher mode...it's still Mommy mode, only now we're doing Math together..