Unless you have another planned use for the spool, you can pre-load the SMB and spool together, and then you don't have to deal with the line underwater.
I find the oral inflation technique easiest because you are simply transferring the gas from your lungs to the SMB -- adjust your buoyancy to be neutral with your lungs full, put a breath in the SMB (you're still neutral), let it go and put a puff of air back in the wing.
If you inflate from a reg, remember you are ADDING lift the whole time you are doing it, so you have to have adjusted your buoyancy accordingly.
I find the oral inflation technique easiest because you are simply transferring the gas from your lungs to the SMB -- adjust your buoyancy to be neutral with your lungs full, put a breath in the SMB (you're still neutral), let it go and put a puff of air back in the wing.
If you inflate from a reg, remember you are ADDING lift the whole time you are doing it, so you have to have adjusted your buoyancy accordingly.