My experience with field rifles is that they are subject to use and abuse that a bench rifle, for example, might not see. So they all develop a personality sooner or later, ie dings, scuffs, scratches etc.
So you have to ask yourself, am I trying to come up with something that is impervious to signs of use??
Or should I come up with something that can be touched up from time to time??
On the wood stocks that I have painted I took a small hand held orbital sander and stripped the finish off down to bare wood. Don't just rough it up, strip it.
If there was checkering I taped it off to keep from sanding it. Then I would hit the checkering with laquer thinner to at least clean if not prep the surface for a primer. On the last rifle I did I got some sand from my sand blaster and then taped off the checkering in reverse. When it was wet with primer I sprinkled some sand on it. It makes for an excellent grip and you can't tell its there unless you are holding it.
I highly recommend a primer as it will have two characteristics, one is adhesion to the wood, the other is it will be designed to provide a basis for the paint that the paint will stick best to.
Get a top coat that is matched to the primer you use. Spray cans work just fine and if you don't like the result you can always sand it off. There are nearly no true laquers available. Many of the enamels are now of the slow cure variety (24 hours to full cure) and they are tough as nails.