to answer your questions about hands....
I hold my dsmb in my left hand, my spool in my right hand, with the line in between my middle and ring fingers. I disconnect my drysuit hose with my right hand, and push it onto my dsmb (still holding the dsmb in my left hand), let it get some air in, and let the dsmb go with my left hand/disconnect it from the LP hose (although it doesn't lock onto the lp hose for obvious reasons). I open my right hand face down so the lp hose drops and the line keeps running out, but my palm stops the spool from going away. Once the line stops running and my dsmb in on the surface, I pass it off to one of my teammates and reconnect my drysuit hose.
It takes a bit of practice in the shallows to get it right. I normally send my blob up from between 21 and 30m, so it doesn't need loads of gas. Your lp hose won't lock onto the nipple on a halcyon blob, so it will start to take off on it's own. Make sure you're clear of any line as you fill it. It's by far the easiest blob i've used (except in winter when my hands are numb)
Edit: you must pull back the collar on the LP hose, or there will be no inflation