Will a simple drill make a clean hole?
I guess it's not horribly important but I would like to know what your results looked like.
All of my prosound holes, save one which used a combo of screwdrivers/exacto knife, were done with a simple drill from Target, and the largest size drill bit in a standard set (1/4"). If there is a little plastic residue, you can easily cut it off with an exacto (hell I've even used a steak knife in a pinch, it's not hard plastic). Going to any hardware/omni store (target/ wal-mart etc) and you could ideally be set up to be making super clean holes for prosound for around 20$ max. And as was mentioned, if you pick up a used drill, you can easily cut that in half. An exacto knife shouldn't be more than a few bucks. A lot of times they are 99 cents near the register at ACE hardware.
On top of all of this: If doesn't have to be that clean. The tiny metal ring that secures the jack in place covers most small imperfections that might happen (though Nitro2K01's picture is not an example of this, his does look damn sexy). Also I agree with what Herr Proff said about doing a small guide hole first. Again, if you get the cheapo/standard 5 bit set from target, the tiniest is the best for that. I think my set was like $3. Something stupidly cheap and it works like a dream.
Good luck!