Pretty much covered it
However I wouldn't hold by the fill whip
It does seperate your hand from the cylinder if something went wrong, but it can put a strain on the fitting
I recommend cupping the regulator between two fingers and hanging the cylinder and gun
If anything blows then you are less attached and out of the way of whatever ends go up or down
When actually filling I also say not to do just one press to fill. Fine if just topping up
If you're filling from low or empty then press the lever for a short while, release, pause, press again and repeat
3 goes should be sufficient
Touch the cylinder and you will see how hot it gets and with experience you will begin to hear how fast it is filling
A fast fill will heat the cylinder which at least just means you get les of a fill (hot air expands so when it cools you find that you have less air - fill when you exit the game and check/top up before going in)
At worst a fast fill generates the heat to increase the chance of a flash fill
High speed fill stations stopped back in the day when there were the flash fill explosions in the UK, but they may creep back
Also there are now fast fill nipples so you can get a pretty fast fill from a standard station
Flash fill failures are a rare thing so not a major worry. Just be aware and we won't be having anymore