One tiny nuance that might help: If you're using a full Eastern or stronger, make sure your hand is all the way down to the buttcap. Specifically, the length of your little finger should be along the edge. Aside from effectively making your racket longer, the width of the buttcap should make it easier for the handle to fit snug in your palm.
Also, if you're on the tall side (say, 6'+), you might want to consider using something slightly lighter than Eastern. Wawrinka uses mild Eastern, Dimitrov uses continental. Just something to consider.
And if you can't find a partner or ball machine for a while, try a wall behind a strip mall.