Back on topic, I would say your best bet is to simply try different sizes of screwdrivers. I found that the one I was using was slightly too small and wouldn't turn the head. By going up a tiny amount, I was able to twist the screws with ease.

I doubt if WD40 would do much here. There are also screw-removal tools out there, but I haven't seen them do much good. When I worked at a machine shop a while back, they issued everybody a couple screw removal thingies. None of us ever used them.

-Biscuits