it sounds like you've about eliminated the system being bled by the gallon of diesel on the floor, but i'll throw this out there anyway. do the older 12v cummins have a shraeder valve anywhere in the engine compartment? i know the older IDI navistars do, which makes priming a dry system a breeze if you have a vacuum pump.
pull the stem out, and run the pump a few seconds at a time until you get fuel there. throw the stem back in, crack all the injector lines, and crank till you get fuel at the injectors.
let me know if you need a pump, i have a suitable one you're welcome to borrow.
fwiw, the few times i've tried this only results in building a little pressure in the tank, nothing else. i don't think the rags offer enough of a "solid" connection. again, my only experience in this area is with IDI navistar motors, could work like a charm on a cummins.
