Once you are through immigration (assuming you are flying in on a non-Schengen flight) you can follow the signs to 2F and there should be no problem using that lounge, even if your onward flight is from 2G. The showers in 2F are more convenient (self-service and unisex), and there are relaxation rooms for napping. If you get there early enough and plan to spend several hours in the lounge, you might even score a Clarins spa appointment, although I personally still understand this to be a completely imaginary offering.