I have a couple of 3's and a 12. I've got a lead with screw in connectors that stays on the 12, and i just use a set of grips to nip it up to stop any leaks. Do it slowly and you won't build up heat. Keep the lead short enough to be efficient and long enough to be easy to use. Advise a gauge on each bottle. But it saves a lot of £. Local dive shop was happy to talk me through it, but as long as you're methodical and pay attention, you should be ok.
BFTA/NSRA County Coach
CSFTA Chairman/BFTA Rep