I usually soak my lines in warm water with a little Ivory dishsoap, rinse, dry, apply 3M line dressing and wind back onto the spool. I know of guys that have used Armor All and some STP protectant, but all of the major line manufacturers discourage this. The phrase "deplasticizes the line" comes to mind...
I'm not saying those protectants don't work.I'm saying 'I don't know". I use Armor All on my boot foot neoprene winter waders. I know that the same manufacturers also want you to buy their brand cleaners and dressings. Fly lines cost a lot and I don't want to dress them with anything that I'm not sure of.