I'm planning on coming in via an old abandoned trail from Horseshoe Meadows -- along the South Fork Cottonwood Creek (Some maps show the old trail), then over New Army, maybe tag Langley, then on to Sky Blue.
I did that exact trip - including taking the old SF trail & tagging Langley along the way - around 5 years ago. There's a short-cut down from Langley to upper Soldier if you don't mind glissading on your feet through shin high sand & scree:
Actually, it was sort of dumb to do in trail runners; mountaineering boots + knee gaiters would have been ok. The normal route is to descend back towards the Army passes, then turn east down to upper Soldier.
I think all this discussion about Crabtree pass is making it seem more involved/difficult than it actually is. I've been over it two times, and it's really pretty straightforward with easy ramps and solid rock. IMO, the last 1/2 mile of Shepherd pass (which I've been over a handful of times) is at least 2x as difficult, and it's technically an (unmaintained) trail. It's just that it's really loose boulders & scree, and pretty steep.
Crabtree seems to be increasingly popular. The last time I was there, there were a bunch of tents parked right on the top of the pass (there's a very big plateau on the Sky Blue side) that a boy scout troop had left. My guess was they were summiting Whitney via Discovery.
This shot looking down makes it seem steeper than it is. The ramp route down is to the right of the photo. It's an obvious route to the north-east edge of the lake, by which you traverse around the north side of the lake itself:
