I have 2 spare slots on my CO2 system, and I came up with this idea for rapid carbing a keg: Build a system similar to what commercial breweries use to carbonate beer. I haven't built this yet, but I think it's worth a try:
Beer line to 1/4" barb x 1/2 inch NPT from full flat keg to 1/2" NPT Tee
CO2 line to 1/4" barb x 1/2 inch NPT from CO2 supply to 1/2" NPT Tee
Beer line to 1/4" barb x 1/2 inch NPT from NPT Tee to empty CO2 purged keg
Connect ball locks on each keg, and gas line to CO2 supply, open line to full keg first, then CO2 supply. Transfer at ??? PSI, releasing CO2 from carbed keg as needed. Clear beer lines will show bubble flow.
Keg to be filled would have to have IN/OUT switched to place fresh beer in through the bottom of the keg, and would need pressure released to switch back.
I know rocking the keg is simpler and cheaper, I'm not sure about faster. The advantage of this method would be setting CO2 for ideal carbonation with very repeatable processes, much faster than "set it and forget it". The disadvantage is wasted CO2, more person hour time consuming than "set it and forget it".
Is it worth it to spend a few bucks on this experiment?