Have you taken the BART out of SFO?

How EXACTLY do you get from there to Millbrae? I know I have to take the AirTran to the G area to catch BART then I have to go north to San Bruno, change tracks and go south to Millbrae (the shuttle was closed) but can anybody who has actually done this tell me what the train signs say? Will one ticket do okay or do I need to buy another one at San Bruno? Thanks!