To descend walk up to the top of the buttress and pick up the trail that heads down into the drainage. The guide book says to go up a little bit to pick up the trail. The ground was snow covered and we ended up going too high and had a really shitty bushwack. You shouldn't need to go very high at all. Managed to pick up the trail again after a bit. Anyhow, the trail heads down into the drainage on top of Cascade falls. The trail resumes just shorty above the top of the falls, should be easy too see. Follow the well beaten path down without problems. Pretty straight forward.
The climb itself sucks but the views are fantastic.