I spent yesterday on the Mitchell (with a lot of other people!) and had very good luck.  Caught about 40 or so.  There were a lot of caddis, and some mayflies, in the air and on the water, but I didn't see any rising and only a few jumping.  Some nice big rainbows (18 inch?) and brookies.  Best luck on the flat water near the parking lots, and in some deep holes.

Red copper johns, and bead head caddis pupae in tan or green.