I don't know Bronicas from a bar of soap, but since you have a hot-shoe on it, then you can probably use any old hotshoe flash therein. The warnings about extra connectors pertain to more modern (with TTL metering, etc) flashes that have more pins on the bottom of the flash foot. Some hot shoes can short out the control pins on the modern flashes and make them malfunction. A bit of insulating tape to cover the extra pins will generally solve that problem.

Getting the flash exposure right without a flash meter or a digital camera to preview your exposures is very difficult. You can get flashes with "A mode", which have a light sensor in the front of the flash. They work semi-automatically on any camera, you just need to dial the same ISO and aperture settings into the flash as you do into the camera, and the flash will make the exposure decisions for you. Apparently it works OK for negative film and with bouncing but I've never tried it and wouldn't trust it for a portrait session that mattered.

It might be best if you didn't use flash in this specific case, just for lack of the right tools. You'd probably be better off going outdoors and using a nice big foil reflector to balance the light.