I use 1/4" Ebony and Holly for the inlays, I get the patterns from old Weatherby and Winslow catalogs. I copy them and expand them up/down or sideways with the PC, cut them out with a scroll saw and do most of the inlay relief with a Dremel tool with a router attachment. The shading is done with an engraving bit in the Dremel tool and filled with a mixture of ebony sanding dust and TruOil. The Dremel/router tool is also handy for inletting the action if you are stocking from the block, or one of the C'alico Hardwood Weatherby seconds. As a note I do the panel carving just prior to applying the final finish coats (about 3/4 of the way through finishing). I use Birchwood Casey's Tru Oil, tried a spar varnish on the Arisaka and was not happy with the results.
Enjoy!