I've had very similar issues and think that ML's Alkalising drink works wonders.
As you say you (or I in my case) feel very depleted, after the third flush I did I started replenishing with the drink to ensure my system has a nice influx or essential minerals in a well balanced form.
Also exercise helped me alot, and continues to do so, getting the lymphatic system moving better, which means a further need for restocking of vitamins/minerals.
I'm doing flush 7 this weekend and am now feeling well enough, energy wise, that I am more looking forward to it than seeing it as any sort of chore.