With Brendan's help, an ankle harness, rope, and pulley, Rob Miller performs an "elevator" on the rings. Starting from the inverted hang and with a false grip, curl the rings to the shoulder stand, then press to the handstand. This is a "C" move on the gymnast's scale where "A" is easiest and "E" hardest. (The muscle-up is an "A" move.)
Alternatively, the elevator can be developed without rings and standing by curling a pair of dumbbells, again with the false grip, and pressing them to overhead. When you can do this with dumbbells totalling your body weight you'll be close to ready on the rings.