I haven't tried it, but I bet it's a piece of cake. Firstly, it's just CO2 and water so the only question is how many volumes to push in there. Second, if you just swap the CO2 line between kegs, you don't need a dual gauge regulator. Once you've got the seltzer the way you like it you can disconnect the CO2 line, at least until it needs a little more to help push it out. Finally, I can't think of any technical reason you'd need a fridge, if you don't like it warm you can add ice, right?