Alright, I'm not going to read a bunch of bull-shit FandF comment's, I know there has to be some.
Double-clutching is pointless in racing. Maybe your friends were joking you or something but how do i know? Well, IF you want to shift faster and don't give a shit about your synchro's in your transmission, Keep the gas floored and stomp the clutch in with rapid gear change and let out once in gear. Unless you have money to replace your tranny I just recommend easing your car into gear, kind of quick but not enough to harm your transmission. Trust me
I've payed for that mistake, well not really a mistake. But I would like to eat up gear's, chirp each gear during shift changes just to keep up but for what? A simple "fun" race that your not getting anything out of...not worth it bro..