The way the builder images work is, you flash them using the tools (eg. the "wizard"). Then, they run the next time you power cycle the empeg, no wizard required. Actually, not just the "next" time, but EVERY time from then on until you install an empeg software image over top of it.

So if you already have flashed the builder image, then just hook the serial port up to a decent comms program (eg. ckermit) and capture a session log with that. Power on the empeg once everything else is ready.