Here is the rough outline for brain tanning a deer hide, as I learned it at Way of the Hunt

1. skinning: front of legs, back of legs. (30min-1hr). Peel, don't cut.
2. fleshing: scrape off the fat & meat
3. preserving: salt or freeze the skin.
   1. salt:
      1. hair side down
      2. pour on & rub in salt
      3. fold over, roll up
      4. put in bag & tie
      5. poke hole in bag
      6. put in bucket w/lid
4. Alkaline soak: use 4 inches of wood ash in the bottom of bucket, fill with water (2-6 days [done when hair falls off])
5. graining: scrape off fur and grain (1-2hr)
6. soak in creek for 1-3 days
7. balance PH: 1/2cup apple cider vinegar to 4 gal water in bucket. stir hide for 15min
8. dry: hang to dry for a bit, then stuff into a bucket with holes on the bottom. hide will dry to form inside the bucket
9. wait: let it sit for 2 years
10. Brain solution: 1-2 brains per hide. slightly cooked, then blended
11. soak hide in brain solution overnight
12. wring and drain 3 times until there are no drips
13. stretch and work all day until soft, and a finger poke bounces back
14. smoking:
    1. sew holes
    2. glue edges together into bag shape
    3. hang and attach to chimney
    4. smoke both sides for 1 hr
    5. use punky hardwood
15. ventilate: thoroughly air it out, or else the smoke smell will make you sick