Nail hole filling for chestnut trim

[Rho1107]

Folks at OHW:

New to the forum.

I am in the process of restoring American chestnut interior trim boards on a 1926 Colonial home. I have the boards stripped of paint/varnish (I am very lucky that the boards are flat and I could run them through a planer/jointer, which works quite well I must say), and am now ready to reinstall them. Most boards have many nail/screw holes from finish nails, window shade hardware, etc., which need to be filled either before or after reinstalling them on the doors/windows. Any advice for filling these holes to make them as unnoticeable as possible?. Most holes are smaller than 1/8 inch diameter.

I do have the option of filling holes first, sanding the boards, then putting on polyurethane varnish before the boards get reinstalled. But I will create a few more holes when I reinstall the boards with finish nails, so I will still need to fill those post-installation. I'm going to try to re-use as many of the finish nail attachment holes as I can but expect that I will need to create a few new finish nail holes.

Thanks much

-R