It is easier to separate the glass from the frame at the non cracked/broken end first. I kept my fingers near the end I was heating up - this is a good way to ensure that you are not overheating the plastic. I also used the low setting on the hair drier. This step wasn't too bad, it just takes time and care.
A final tip is there are some small spring contacts behind the home button that look easy to damage. Be careful not to catch these and bend them, especially when working to separate the glass from the frame. If these get broken the home button won't work.
All went well, but I should mention that the force required to pull the screen off is much higher than I expected. I kept one hand wrapped around the top of the phone to make sure it didn't fly apart and damage the connectors to the logic board. The other trick is to get the suction cup as close as possible to the button to increase the leverage. In the end I taped over the home button so I could use the suction cup at the very bottom. Keep an eye on it and after a while of constant heavy pressure it should start to separate.