I now (having only just heard about it yesterday bizarrely enough) prefer the hollow leadcore method
The ends must be gently burnt before threading the line through (this gives the top bead a slight buffer to stop it being completely free running)
The top bead can be plugged with a bit of spaghetti or better still a piece of PVA solid stick if you are using a big lead, big bait, or PVA mesh bag
And the bottom of the leadcore sleeve must be glued to the bottom mainline knot or tied with the mainline
I never put any sleeves over swivels on at the lead end, to me it looks tacky, bulky and obvious, it is swivel off, plug a 6mm rubber bead over the wire loop and put another rubber bead above that = perfect minimal buffer