I rode most of the rest of the BAM route this week, staging out of the Elk Creek Trail Head. It seems the best route (there are several depending on where you are coming from) to the trail head is to hit Sturgis on the way and head up Vanocker Canyon, making a left on Runkle Road. The trail head is a few miles down this gravel road. The other options are either narrow and gravel for many miles or narrow, twisty and tourist-laden.
This is great riding in both directions, rough and sometimes tough, but excellent.