I'm not sure about the canon flashes, but the Nikon ones have an option to go off TTL and onto regular old fashioned autoexposure with the built in sensor on the flash like an old vivitar 285hv or something. This is great for bounce or modified flash. Then there's another option on the flash for full manual where you set the iso, aperture, and it indicates a distance that the power setting is suitable for. Adjust power setting or aperture for different distances. I think you'll find B&W film to be more forgiving than digital in terms of exposure; a little overexposed is easily tamed in B&W, but often not worth keeping in digital. I have a minolta flashmeter IV which is now $100+ish used and it does a great job for flash, flash+ambient, or ambient exposure. And you'll really look like a pro wearing it around your neck.