I've gone through my old kit and found a Canon Speedlite 199A. Will this work as a "slave" flash if used with something like a Pocket Wizard?
As long as you can trigger it, yes, it should work if you set it up right if it has the proper capability to do what you need. But I know little to nothing about the operation of that flash. I am referring to whether or not you can safely use that model flash with any DSLR. There is a website that shows what flashes ARE and ARE NOT safe to use on the hot shoe of a DSLR (because of the trigger voltage). According to that website the Canon Speedlight 199A IS CONSIDERED to be safe for use ON a DSLR, so your flash can be used either on or off-camera. Maybe you can find operating instructions, or a review of the flash somewhere online.
Yes, it should work as a remote flash. I don't recall the details of that flash...but I don't think that it has manual controls. Meaning that when it's not connected to a compatible camera, it will fire at full power every time. That's OK, at least it's consistent, but it's not as versatile as a flash that has manually adjustable power.
Also, some flashes may go to sleep after a set time when mounted on a remote trigger. I had a 420EZ that do that. And the only way to bring it back up is power cycle the flash.
