Need assistance setting up air tank

Hey all,

I am trying to help out a buddy of mine. He is not very technical, but he is a great shot, and loves air guns. He has an older Air Arms S400MPR that he has been shooting for a while. Well, last year he bought a Marauder. I was talking to him the other day, and found out he still hasn't shot it!!!! I find this quite appalling. His reason: "He didn't know how to fill it." I quickly looked up online the instruction manual and figured out it takes a Foster 12FS fitting. Looks like a quick connect to me. I found them on Pyramid, but his issue turns out he doesn't want to mess around with changing out fittings every time he swaps between filling guns. 

I figured he could just put a female QC on his hose from the tank and then add a male QC to the fitting he uses to fill the Air Arms. Bummer it doesn't appear to be that easy. To fill the Air Arms, he removes the cylinder from the gun and threads it onto a fitting on his scuba tank. There is not hose or anything so my QC idea won't quite work. Any ideas on what I need to get put together for him so he can easily swap between filling both guns?

If I could figure out how to add a picture, I would include a picture of the tank and valve setup he currently uses with the Air Arms.

OK, I watched the tutorial. Here is a picture of what I have now. The Air arms cylinder just screws into the brass fitting.

http://i.imgur.com/klAqPjv.jpg