I could try to swing a hammer back there and pound the bolt in, but that seemed to lack elegance. So I decided to pull the bolt in instead.
I stacked a bunch of oversized washers and put one of the new lug nut on backwards so the flat part of the lug nut would rub against the washers. This worked great at first, but when I started to apply actual force to the wrench, the whole wheel hub started to rotate.
So I got a long pry bar and slipped it between two wheel stud bolts and against the ground. That locked the wheel hub in place so I could apply some force and pull that new wheel stud bolt into place. It worked beautifully.
Here's the first new stud snug in the hole! The second one was even easier because I knew the routine now.
And I cleaned and sanded the brake rotor a little to get rid of some of the glazing on the surface. There were no deep ridges at all, so I could reuse it without resurfacing it.
Oh, hey. This is a good picture where you can see the piston in the background. It's that silvery looking cup with the rubber gasket surrounding it. It's sticking out pretty far. As the old pads had worn down, it pushed out farther and farther. I'll need to compress it to make room for the new thicker pads to be installed.