I've never been able to make it do this in several tries. I've built custom IPSW's for 3.1.2 and 4.0.0 and have installed them in a few phones but every time I have to go through the whole build process for Pwnage to kick the phone into DFU mode.

If I click on the 3GS phone model and then click on the DFU button, it says "connect device to USB" and never goes anywhere.

If I go through the build process, it delivers the payload to get in and then tells me to start up itunes and load the new custom IPSW.

What am I doing wrong? or did I miss something?