Well, the weather has been too good not to go climbing, so I headed down to Donation yesterday afternoon. Much to my surprise, I had the whole place to myself.
The picture (not very good) shows the rope solo system that I used. This is my first time using the Peztl MiniTraxion for this purpose. (One advantage of having climbed a couple of walls is that one has a lot of interesting gear to play with on an occasion like this.)
Steph Davis has a good post on rope solo systems (and the follow-up comments are helpful too). What I did was tie the climbing rope in to the anchor at its midpoint, with a figure-8 knot on a steel biner, so I had two independent anchored strands. One strand went through the mini-traxion, which rode on a full strength chest harness (also clipped to the sit-harness by a short sling). The other strand went through a Gri-Gri.
When climbing, the mini-traxion side was weighted to my gear bag and then fed automatically. the Gri-Gri side I pulled rope through when convenient, and also tied off with a separate backup knot every now and again. To transition to rappel, just open the cam on the mini-trax and rappel on the Gri-Gri.
At first I was pretty nervous trusting the system and moved very slowly and inelegantly. But it soon became clear that it would work fine. The pulley moves up with you and gives a good catch. Still, I should probably have started with something a bit easier. Things feel different when you are the only one around!
If working something steep, one should carry prusiks so as to be able to unweight the mini-trax and transition to rappel when hanging in space. Of course, one could bring ascenders; but that seems to be taking the idea of raiding the aid box to an unnecessary extreme!