That link to Doc's didn't work for me
I've used a nitro setup on a scuba tank to fill. It's dead simple!
1) Attach your fill nipple to the fill "plug." (Make sure you have it on tight. I scared myself and some kid when I tried to fill his Flatline on Sat and didn't have it on all the way. POP!)
2) Turn knob on fill station.
3) Watch guage and listen. You can hear it when the tank is as full as it'll get.
4) Turn off fill station knob.
5) Bleed off the air. Some stations have a button that releases the air. Others have a knob you open and close. You'll hear the "shoosh" as it bleeds off.
6) Remove tank from station.
Unfornately I don't know how to attach the station to the scuba tank. Sorry