ossage,

What I was thinking with the dowel plugs is you could slightly drill them out to smooth out the grooves left by the screws that attached the quiver.

You can pick and choose your grain when doing plugs, instead of buying dowels, you make them. Align the grain accordingly. I am thinking quiver holes are small enough you'd have to really look over it hard to see it. You could also find a piece of wood similiar in color to the riser wood before plugging. If he's painting green over it, grain wont matter and this would prove the simpler of the 2 methods. Burnish the plug before putting in so it fits snug, add your glue and it will sweel slightly filling the hole nicely. I dont remember how many of these I had to do on my strip canoe, but you'd be hardpressed to find half of them once they are sanded smooth....

I really like the epoxy and dust method but have some reserves about painting over it. Its very simple and effective. You might be able to put on some automotive touch up paint over it to match the surrounding paints. Concerns would be compatiblity.