I've been wanting to get into off-camera flash for a while, but not really sure where to start. I've done a lot of reading, and looked on Strobist, and the Flickr group for Strobist, but I haven't found the answers to everything yet, and I was hoping for some help. I've been doing a lot of nightlife photography, and know that a second off-camera flash will fill the shadows that I often get with only one flash, but I'm not sure how to do it, and if I can with the equipment I have now. I have a Speedlite 430ex and a Sigma EF 500 DG ST. Could I use the Sigma as a master on my camera and then the Speedlite as the hand held one, or do I need to have two Canon flashes? Can I use a wireless transmitter with my 40D? (A friend was trying to show me how to do this, but his wireless thing didn't work on my camera.) If I can't use a wireless transmitter, can I use a regular hot shoe cord? Constructive comments and responses are greatly appreciated. Thanks!