How do I insulate an existing, finished garage?

[jkuro]

As said above. Attic first. Door second.
Walls last. Instead of holes I prefer to cut a 6 to 8 inch slot just below the top plate. Fill with blown in insulation, finish top with fiberglass bats. Cover slot with 1x6 or 1x8 trim.

 

[Pexto]

A question for those who know about blown-in cellulose: Is it possible to successfully blow additional insulation into a wall that already has fiberglass batts in it?

I'm hoping to improve the insulation in a house that has 2x4 walls with kraft-backed fiberglass batts in it. There's no vapor barrier, just sheetrock inside and plywood sheathing and siding outside. From what I can tell, the batts were stuffed somewhat carelessly into the wall cavities, with no attempt made to cut and fit around electrical boxes, etc.