Originally Posted by simplify
Since these are "grab" shots, I would definately shoot available light if you can. Work with your camera with available light first, to get the feel for what you can do with it and what you need in terms of lighting. Once that is done, you can then tell if you will be needing to use flash before you pull out the camera. If you need to use flash, go ahead and use a bulb but be careful, when you get closer to people it would be wise to have a flash shield so you don't spray glass if one of your bulbs shatters. That doesn't happen often but it does now and then. I suggest using the guide numbers for your bulb and film choice as a start. You can do a flash test to get your true guide number but that will take some bulbs. Or, you can get a Kodak Pocket Guide which has a bunch of information on using flashbulbs and has calculators for flash. Get one of the ones that came out in the mid 80's or earlier. A wealth of information. They show up on WePay often.
Speaking of bulbs, the #5, Press 25's #6's, and FP 26's are available as are the M-2's, M-3's (ok to use with a ring clip adapter for your gun) in blue and clear flavors. Prices vary wildly so keep an eye out and you can get a good deal for them. Maybe Mr. Duffy can offload his to you for free?
Using bulb flash is a gas and I find that when I pull out my fash unit and Speed Graphic, people tend to want me to shoot them.