I was supposed to post this after my Tau painting weekend, but time gets away from us all.
Here are my thoughts on painting a large chunk of an army in one go, which in this case was a short platoon, but could also have been a large-ish regiment, or a full skirmish warband (provided that the colors are restricted).
First, better lighting is needed, particularly when removing mold lines. Failure to remove all the mold lines will be annoying when the project is closer to completion, so better to spend the time up front and do it right, and it will be easier with better lighting.
Second, get some proper seating, and if you are going to be sitting for 7+ hours as I was during the primary painting session, then you need to mix it up a bit. My back was sore afterwards, and I spent part of the time sitting on a yoga ball to help mitigate this. Proper Posture Prevents Pain!
Third, proper base coat planning will save time. Had I used the main armor color as the base coat for the whole miniature, it would have saved a couple of hours of time. I could certainly have found a flat olive green for this project, and at Walmart or similar it would have been pretty cheap too.
Fourth, and this is something I knew but did not take advantage of, spray coats of primer and/or base coats will save time over brushing. I brushed gesso on the figures, and it took some extra time and is slightly thicker than spray paint would have been.
Fifth, it is faster to paint by part than it is to paint by color. By this I mean that painting a single color on all left legs and then right legs and so on is faster than painting all of the parts that use a certain color, and helps to prevent forgetting to paint the hoof of the left leg on a certain miniature or something.
No painting progress lately, as we had Thanksgiving/family/illnesses to get in the way, but I did get in a game of 7 Wonders, and spent a happy 20 minutes fitting together another random Inquisitor warband figure.