The rear delts usually get neglected, but this is a pretty easy fix and one you can do at home on a daily basis. The band pull-apart will bring your sad little finger-sized rear delts up to snuff quickly.
You don't need a heavy-duty resistance band because you're going to keep the reps high. Rock bottom rep range is 20, done for 4-5 sets daily.
Not everyone was meant to squat deep, but a simple test will tell you how deep you can safely go. And if "butt wink" is a problem, there are easy ways to fix it.
Certain things look good on paper, but most don't pan out. For instance, Eric Cressey thinks wave loading is a bunch of hooey, as are weight gain powders and, believe it or not, the notion that external rotation movements are a cure all.