While I am generally supportive of jigs, I have a pair of nut plate jigs and I consider them useless.  Drill the hole, stick a short bolt thru the hole and screw it into a nutplate (finger tight is plenty).  Orient the nutplate the way you want it and drill a #40 hole through one ear (essentially you use the nutplate as the jig).  Stick a rivet in there and drill the other hole.  Remove the screw and countersink the rivet holes.  You might then want to drill out the screw hole a few thousandths for easier assembly.

Note:  If using a floating nutplate, get the floating part kinda centered when you drill the first hole.

I've never had any problems doing this.  My bigger problem is setting the rivets to attach the nutplate -- it's not my best skill.  I have drilled out a few of those and started over, but the original rivet holes were fine.

- Rob Wolf