I used the baffle things stapled to the underside of the sheithing to ensure good ventilation. I ony did this on the bottom 8'. Next I ran 1 horizontal row of OSB for the start of the ceiling. I was able to poke the thick *** insulation down to the eaves. Next was a couple more rows of OSB. Repeated the previous. Do the same for the other side of the ceiling. I'm very happy with the insulation. The snow stays on the roof and very little ice developes at the edge of the roof. The only time I get icecycles is when the outside temp gets above freezing.
Non of the insulation is in contact with the bottom of the roof. It all sits on the OSB that I used for my ceiling. I remember the insulation pieces came in 8' sections. I was able to poke half to the eaves and staple the other half up in preperation for the next run of OSB.
Roll around scoffolding was very helpful as well as a ground person to hand you the insulation and move the scaffolding.
The best? Icenyne. It's what I will be using in my next house. I've done several homes with it and it is a HUGE upgrade over traditional batt insulation. There are several other brands of open and closet cell insulation, however Icenyne is the most recognized.
Another option would be to use SIPS panels for the roof deck. Probably would look the best from the underside.