Check out the DVD
"Turning Deerskins into Buckskins" and you will probably never want to try it.
It's an unbelievable amount of work. He shows how to do it with modern chemicals and how to do it the way the indians did it by "brain-tanning". You use the brains in a mixture in the preservation process and use some ashes from a campfire in another solution later. To make sure the surface tension(I think that is right) you have to float an egg in the solution until just enough is above the ash water. It wore me out just watching it.