Tough question. There are books written about this. Tru-oil on it's own can tend to be shiny, depending on how many coats. You can alleviate this by either rubbing with 0000 steel wool or using something like Birchwood Casey Stock Sheen and Conditioner on top of it. How you want the wood to look is really a matter of preference. I'm going to be refinishing a repro. 1803 Harper's Ferry and I plan on an open-grain look. For this, I'll stain the wood, then just use boiled linseed oil. A friend of mine mixes dark tung oil with the BLO for a darker finish. Another option is LinSpeed oil.....believe me, every person will give you a different opinion. The good thing is if you do something and hate it, you can strip the stock and start over. Check out this site. Folks there may be able to help you in regards to the particular "traditional" finish for the LGP...
http://www.muzzleloadingforum.com/fusionbb/index.php?
http://www.muzzleloadingforum.com/fusionbb/index.php?