go to dixie gunworks online and order their catalog. they are the definitive source for tools, supplies, browning/bluing solutions, wood treatments etc. I built the great plains percussion gun back in the 80's and it is a terrific rifle. The 1-66 barrel pretty much limits you to roundball, but it will kill a deer, and turkey easily. You can buy the same gun (or the barrell alone) with a 1-48 twist iirc that will allow you to shoot saboted slugs or the maxi and mini ball loads which are very accurate and deadly as well.
I used a 50-50 mix of tung oil and boiled linseed oil on mine. Put the stock in a cradle, dab on some of the mix, then use some burlap coffee sack and "shoeshine" the wood till it heats up hot to the touch. Repeat till you have about 10 coats on all of the stock. It is work, but well worth the result.