Thin Acraglass wtih Acraglass thinner & solvent from Brownells. There are some other commercial epoxy thinners available & I have been told that solvents like accetone will work but have not tried this myself. You can get Acraglass as thin as water with the Brownells product.
I've also read somewhere that thinning with solvent degrades the bond & strength of the epoxy somewhat but I don't know that for sure. It doesn't matter anyway if the thinned epoxy is being used on properly done inletting as a moisture & oil barrier but if you are using epoxy to correct issues such as cracks, wood defects or poor inletting you may not want to thin it.
Please don't try this on something nice like the Purdey example until you have done it a few times on something that does not matter & you are still going require a very very thin release agent on the metal even though 99% on the thinned epoxy will soak into the wood you still should assemble the metal to the wood while it cures.
I've done this a lot on rifle stock inletting including under the butt plate or pad & on some of my shotguns. It's a PIA to do on already finished stocks & you need to use some care.
