I tan my own leather, and use the brain tanning method... but in place of brain i use Murphy's Oil Soap... (i've seen it done with all types of things including eggs and mayonnaise as well as a bar of ivory soap that had been dissolved in water...)
there are many video's and guides to brain tanning a hide... i recommend buying a draw knife and using the wet scraping method... it's a little more repulsive but scraping is MUCH easier this way...
http://www.youtube.com/watch?v=osY7ZS2FjgM the scraping rig you see set up at 2:45 is VERY nice and makes life sooo much easier...
the most important step in the whole process is breaking the leather... that is what makes the leather soft and pliable... so be prepared to build yourself a frame so you can stretch the hide on it...
it is true that you wont be able to use buckskin alone for armor, but it makes a fantastic bottom or connecting layer for complex sets, and it can be very soft and durable... you can also get cowhide from local slaughter houses for quite cheap and tan them this way as well... just plan on doubling the work because of how thick and tough they are