I used one of these
http://www.canadiantire.ca/AST/brows....jsp?locale=en
You do have to cut down a Philips head bit to fit in the shell. Another choice would be those 90 degree screwdrivers you can't find anywhere.
Now they say you can punch out the disc opposite the selector switch to use a normal screw driver. Mine sure felt solid so I just left it. I hate messing with interference fit stuff if I don't have to.