[kiryandil]

Mix the fine sawdust from the sanding of the doug fir with lacquer, to the consistency of runny baby poop.

Use a putty knife to pack the cracks in the floor, then do the hand sand after the lacquer/sawdust mixture dries.

Vacuum once again.

Lacquer is pretty nasty, so wear a respirator.

[1_Rain_Drop]

Thank you VERY MUCH for the lacquer/sawdust hint.

I do have a respirator which I love. It has interchangeable parts, one for dust and another one for fumes. Works great since I can't smell anything till I take it off.