Driving Mega2560 from external 5V bricks USB port

The really frustrating part about this is that I know if you have the right files to burn, and the correct abra-cadbra spells to invoke that this 'reload' everything is a 5 minute procedure, and so far I bet I've burned up 6-8 hours over the last couple of days trying to find the correct magic spells to no avail...