I am refinishing 80 year old fir floors. There are some bruises that are quite pronounced and round (probably from furniture feet, like beds). I've done a lot of reading and I've tried things I've thought of, but so far they resist most of my efforts.
Read: sand 45° with coarse grit rotating 90° until gone then finish with grain.
Result: I seem to be using a lot of good floor to get rid of blemishes. It seems it would be better to address each blemish on its own or I'll loose a lot of my boards' depth.
My thoughts: using heat gun remove most of the shellac/varnish and then it's easier to hand sand, but it makes a hollow.
Question: Can I fill the hollows with a "filler"? Can I mix a filler using my sanding sawdust? Is there a commercial product that will finish like the rest of the floor after I stain it all?