A couple of things on the east end...
Once you leave East Park Reservoir, heading north along Little Brush Creek, there are no reliable water sources until you get to at least Summit Park. There maybe water in Summit Park where there is a lot of cattle grazing so your MMV there. We only found two options in that stretch.
One, dropping down the north side from Manila Park to Leona Spring, an almost four mile detour and a bit of a climb back up. The other, which we did, was dropping south along forest service road 037, just west of Trout Creek Peak, to Lost Park where we were able to get water from Center Creek. This was about a two mile detour but not knowing the terrain we could have shortened that by going off road into Lost Park but it was late, we were out of water and didn't want to take any chances. The water was good and we spent the night there. After this point water sources start to become more available. We spent the next night at Hacking Lake where water was no problem. In retrospective if we had known we would have carried a lot more water on that stretch.
One little tricky part is after you have left Lonesome Park (which is appropriately named by the way) you're going to cross forest service road 678 from south to north. The trail does not go directly across the road to the other side but rather about 120 yards to the west. It took us bit of time to locate it.
One last thing on the east end. Watch your rock cairns and tree blazes. They are pretty consistent but its easy to lose them. We only got off trail a couple of times but I'm sure glad we had our track on the InReach to help get us back on the trail by back tracking.