Car Photography pointers needed!

[tomfenby91]

Been photographing cars for a while now but want to raise my game a bit and start to get more out of my camera.
I really need some advice on flash as that's my weakest area, got my self a basic set of old flash guns to use as slave units and some cheap wireless triggers. Any help would be much appreciated! I have a link on my profile to some recent contributions I've done. All criticism welcome.
And for anyone interested my kit is:
Canon 550D
Sigma 10-20mm (couldn't recommend this enough)
Canon standard kit lens 18-50mm
Canon 50mm f1.8 prime
Tamron 70-300mm
+ tripod, flash kit etc.

Thanks,
Tom.