Yeah, I enjoyed Paddy's TR too (thanks Paddy). I may be mistaken, but I believe that photo is of the switchbacks headed up to the pass right before Raisin Lake. The cross-slope looks familiar, although the last time I did it it was covered in snow and pouring rain. You can see that it's pretty exposed, and if you do decide to go up to May Lake, you can expect another stretch, just without the cross-slope, but you get some idea of what to expect.
The few times we've come down from Raisin Lake that way we've done our route selection empirically; a little bob and weave around things...willing to wander a bit and see what happens. We've done it because we could and wanted to see what it entailed, because it really wasn't any great effort or commitment to. Drainages/watercourses themselves are notoriously hard to follow...tend to be more boulders, steep cuts and vegetation, debris. We used that particular one as a visual reference for holding course only. What we did was go around to the other side of the lake toward the outlet, stayed a little higher and left of it by about 100 yards or so, picked what looked good, went over the rise and kept walking downhill to the SSE. As you descend, you'll have the drainage on your right and a brow on your left, keep to the middle-ish of them. The creek actually ends up just slightly too far south of the Sunrise trailhead, so take a look at what's ahead of you from up higher, take a compass reading if you want to (look official doing it so that the wife thinks you have an natural talent for navigation and is even more impressed), follow it and stay left several hundred yards. Here's a sat image starting at Raisin Lake: zoom and scroll at random.
https://www.google.com/maps/@37.8482255 ... a=!3m1!1e3**what you can do is go to the side of the lake opposite the trail, back behind and left of the far inlet you see on the sat image, get up to some high ground where you can see down the other side, decide together if it's something you feel like taking on. No harm, no foul. Half and hour of your time and a short little hike.**
Waterwheel Falls will have considerably less flow in Sept, but that entire complex of falls is gorgeous anytime and worth seeing. Try to leave your gear at GA and day hike it, leaving early, so that you don't have to climb back up with a full load on and do what you can to beat the midday heat. But talk about staying hydrated! That canyon is blazing hot, and once you come out of the trees above California Falls, you're in all the direct sun and reflected heat that it has to offer. Still, worth an extra night at GA to see. Lot's of places to swim, and if you leave part of your food supply at Sunrise, you'll have plenty of room in your can for it.