I have been trying lots of different flash setups lately (optical, radio, bounce, etc), but I tend to fall back on optical triggering because it is the most trustworthy and versatile of my options. Of course, I would love to grab a pair of Pocket Wizards, but hey, you donate a pair, and I will certainly put them to use!
If you have a normal flash mount (just found out Sony uses their own “standard”…punks), you can easily buy a little optical trigger for no more than $15. You slide that baby on the bottom of your flash, and then when any other flash goes off, it will trigger that flash. So, the pop up flash will trigger it, or hey, I have even used my point and shoot flash to set off my speedlight!
But that is not the end.