Check out allergichobbit on Youtube.  I can't get it, due to dial-up connection, but I saw a little and hear it's great help.  You gotta take it slow.  don't try to take off more than a 1/16" bite or so.  I think a lot of guys would be using a purcussion tool @ the start, a golf ball sized rock, sorta rounded.  Get a pad for your seated thigh bone and support your glass against your leg w/ your left hand, protect your left hand too.  The glass will break @ a 100 deg. angle from a 130 deg. blow.  

 how's that for confusing?  Get you some superglue, duct/electrical tape and some bandaids out there too.  

  Check out the Youtube vids if possible, I think that will give you a good idea of what you're after.  Good luck....and watch out that you don't get addicted.  
