I descended from Whitney-Russell Pass last September. There is a nice use-path on the west side leading to Russell, and I descended a nice and loose use path toward Iceberg (East Face) Lake. (I was thinking how nice it was to descend rather than ascend.) I think you will find several use-paths heading to the pass from Iceberg. The use paths lead to a crossing right next to the main Whitney massif, not the areas farther north. Once on the west side, you can easily head north to Russell.
If you descend the MR and ascend to WR Pass, you will definitely want to pick up water at Iceberg. I filled several quart ziplocs with water there so I'd have enough for my overnight on the summit.
I've seen threads regarding your planned route before Whitney. I need to poke around and find them.
