"...You just fish the wire and be done with it?"

Correct. There's no chance of pinching the wire between the wallboard and stud if the wallboard is already up.

This post was edited by glennsparky on Mon, Nov 11, 13 at 4:34

The plastic old work box you install has a plastic retainer piece that holds the wire as it enters the box. In most cases that is all that is needed as long as you are running the wire vertically up between the studs to an outlet higher in the wall.

Bruce

From the 2008 NEC

334.30(B)(1) - NM cable is permitted to be unsupported where the cable is fished between access points through concealed spaces in finished buildings or structures and supporting is impracticable.