For release agent, I use automobile paste wax,,the 'soft' kind. Use a common toothbrush to apply liberally to the metal and let it dry. Never had a problem.
There are lots of other alternatives that people use, but that's just my offering.
On those rounded rear tang ends,,before you apply any release agent you can carefully lay over a piece of common scotch tape, 2 layers if you wish. Just cover the radius of the curve and cut it off as it blends into the straight sides of the tangs. Then apply your release agent what ever it it right over the tape and the surrounding metal.
The idea is that the tape layer(s) will produce a nice even relief of a few .000 at the rear of the tangs to avoid cracking from setback should it still happen.
It makes a nice clean job of it and is easy to do.
Up front you can if you wish very gently taper the sides of the frame inward,,very gently..
That's called draft on the part. Here it will keep the stock held tight to the action and tangs. You only need a few degrees of draft,,hardly noticable and no matter how much you file in, it won't change the side outside contour at all anyway. Only the very small top and bottom frame to wood contacts will show the taper.
Be careful enlarging the contact areas by adding glued in wood at the head of the stock beyond what the metal of the frame is.
You may be trying to boost the strength, but you may block the operation/rotation of the hammers to the rear or sometimes the bolt retracting.
There's plenty of contact surface on that action. Square it up a little to even better make flat surfaces even if you don't add any draft. Careful glas bedding and a full draw on the stock bolt will have it secure.
Have fun with it..
