If you use blow-in and put the access holes on the inside (through the drywall) using a hole saw, the "pluig" of drywall that remains will be a bit too small (loose) to simply just reinsert into the hole due to the thickness of the hole saw bit itself.
If you don't want to buy or can't find tapered plugs try what I did:
I used a 1" hole saw to cut the openings and then used a 1-1/8" hole saw to cut the plugs out of an piece of unused sheetrock. The bigger plugs fit much better than the smaller ones, but were still just a hair smaller than the openings. Perhaps a 1-1/4" hole saw might have been a better choice for really tight fitting plugs.
Either way, it sure was a PITA to cut all the holes, cut the plugs and then mud and sand them all, but I think it was still easier and cheaper that removing the existing drywall, installing craft-faced insulation, and re-drywalling.
I also used a special vapor barrier primer since I couldn't install plastic behind the existing drywall.
Paul