580EX help

I posted a thread for tips on shooting a car show this weekend in chicago. Someone mentioned using my 580 with the bounce card. i was wondering if anyone could give pointers on using the bounce card (i don't know much about my flash yet) to get the best results and what exactly the bounce card does. thanks.

Briefly, you'd pull out the bounce card (which is behind the 14 mm lens) and angle the head up as if to bounce. It'll reflect some light off the card to provide direct light in addition to the indirect of a bounce. Not sure how well it'd work in a large convention center type facility without much ceiling within range. You'd probably want to angle up on the order of 45 deg.

I'm not sure how much light the catchlight reflector will cast forward. maybe use the diffuser panel instead? Or buy a small collapseable softbox?

What you want to avoid is direct flash reflections on the flat surfaces of a car - so angle it at 45 degrees and shoot away. It's more to fill in the stage lights and create a bit of balance. It's not intended to light the subject entirely, just fill flash. Otherwise you will get hot spots, which are a pain to PS out.