I've heard of people using "Joy Dishwashing Liquid" to tan hides. A friend of mine who spent time in Alaska says this is how lots of folks in the "bush" get hides tanned. Joy contains lanolin, which I suppose is the active ingredient that does the job. Another one I have heard of, but not tried is "Neats Foot Oil". I don't know how this stuff is made but, it may have lanolin and other similar chemicals in it in similar amounts to animal brains.
I've seen Indians in the northwest territory use Ivory soap instead of brains in exactly the same manner as the braintan method. That should get you on your way. Check out the film Indian Hide Tanning by Henri Vaillancourt for an explanation on this.