For my paintball co2 setup i bought a fitting thats screws onto the pinvalve on the tank, it has a 1/8 threaded opening. I bought a 1/8 to 1/4 adapter and that screws into a regular co2 regulator. Works really well.
For my portable kegerator i have a square cooler that i can fit an entire coke keg inside of, co2 tank and all with a faucet mounted on the door. And i have another smaller cooler that i cut an opening in the end that fits snuggly a pepsi keg with just the rubber handle sticking out, i like it better because the co2 is outside of the cooler for easier adjustment.