You got it.
Mix sawdust and epoxy, and hope for the best.
Sawdust and epoxy, in a screw hole, tends to cure
darker than the surrounding wood. You can lighten the
mix with bleached linen fibers (micro fibers) ...which
are white.
Make a few divits in scap of plywood and try out a
few mixtures....to see which one works best.
Sawdust from a skillsaw is too course. You have to make
the sawdust with a sander.
To get lots of sawdust, you can go to the local rental
shop, and make a deal with the rental shop guys to save
the sawdust they take out of the
"edger" bags they rent to floor sanding people.
Or you can come by my place and get some.