At the conclusion of 12 Days of the Batman, John Vukelic left this comment:

“12 sculpts in 12 days is a very cool accomplishment. Did you learn anything new working on those 12 busts?”

(John’s site chronicles his process as he learns to become a fantasy and sci-fi artist, and it’s filled with great art resources as well.)

In answer to John’s question: I hate to say it, but I learned very little. But it did reinforce a lot of lessons I discovered with other sculpture sprints, such as Mighty Marvel May, as well as from years of trial-and-error. What I have learned:

Plan ahead:
Particularly when I don’t have a lot of time to execute, it’s much better to have a concrete idea before I start and not try things out as I’m sculpting. I’m terrible about sketching. I virtually never do it, to my detriment. On longer projects, I usually start sculpting and make adjustments as I go. I don’t have that luxury when trying to work this fast, but ten or twenty minutes sketching would probably have helped a lot. Also, making good armatures is always important.
If you get off to a bad start, start over:
If I didn’t make a good armature and started sculpting over it, I immediately regretted it. It actually saved me time to scrap what I’d done and do it over from scratch rather than fight with it.
Keep your materials handy:
Seems obvious, right? I tried to have all my tools, workspace (which was often my lap), and even the camera, light, and backdrop ready before I started. Except I ran out of the Sculpey Firm I use and tried gray Fimo instead (I use a mixture of Sculpey Firm, Super Sculpey, and black and white Sculpey III to make a grey, just-right material). Not the same thing, and it worked- kinda- but the last three or so days I was working with what felt like substandard material. I shouldn’t do that.
Form is more important than detail:
Silhouette, shape, proportion are all much more important to the overall look of a piece than any detail I’m going to tack on. Does it read from across the room? If not, keep working. A rookie mistake- when I can tell I’m choking- is to go to detail too soon. Make sure the form is right, then start finessing.
When working this fast, compromises have to be made:
Forcing myself to put the work up- ready or not- by the end of a day meant I wasn’t going to finish it to my satisfaction. I had to make choices about what was most important and what just had to go. Sometimes happy accidents occurred: I really liked how Poison Ivy’s hair came out in the limited time I had to detail it.
If you do a bad job, you’ll do better the next day:
Sometimes events on the day kept me from putting as much time in as I could, and resulted in some clunkers (I’ll let you decide for yourself which ones I’m talking about). I had to finish them, put them up, and move on, no time to look back.
There is never enough time, so do the best you can in the time you have:
The clock is always ticking. If you have an hour or a month you’ll never finish to your satisfaction, so just work with what you’ve got. You always have right now.

Thanks for the question, John!