I used the "grill pan" I got from Ikea. I love this thing. It works much like a regular grill and cleans very easily.
I didn't use any olive oil or other substance on the pan. I did season each breast before cooking. I rubbed both down with quite a bit of garlic powder and added a small amount of salt and some pepper. I then simply cooked both until neither was pink inside.
They were quite tasty and still juicy. I got slight burn marks on each one from letting them sit on one side a little too long, but it wasn't really noticable in the taste or texture. I had mine with some "chunky horseradish sauce" and it was a good combination.
I've been thinking about trying the horseradish sauce in the preperation stage. I'd mix garlic powder and the horseradish sauce (and perhaps some other seasonings) and rub it on the chicken before I put it in the pan. My worry is that it would burn or prevent the chicken from cooking properly or wouldn't transfer the flavor well. Then again, this is why you experiment.