We would like to insulate and drywall the garage walls to work on projects in the cold winter and hot summer. (We'll probably install a mini-split or something similar, too.) This question is specifically about the walls (but see this question about the ceiling).
The walls are bare-stud uninsulated 2x4's and all work will be done from the inside.
This reference says that if exterior siding is removed to "Drill holes in the sheathing and blow insulation into the empty wall cavity before installing the new siding, and ... add R5 insulation wall sheathing beneath the new siding" ... but we are not removing the siding.
Question: What is the best practice to insulate (and drywall) the walls in situations like this?
Picture of the existing walls: