Without reading through all the entries because the internet is quite slow today, I'm just going to quickly throw in my two cents and leave, but also apologize if I repeated something someone said.
I've used a graflex handheld myself. Mine has a body trigger, so I hold onto that side with one hand, and put my other hand on the bottom of the focusing rail holder, with my thumb and forefinger on the one focus knob. I find that a hand below the camera entirely helps support the weight better than both hands on the side.
If you have a flash unit of the newer style, attaching that securely can give a good hold on the camera.
Now, if you attach a side flash and a solenoid, you have a more comfortable grip and you can push the button on the flash to fire the shutter, you don't even need bulbs.