Since every leg is a little different and the tail section isn't perfectly symmetrical, I have to basically custom fit each leg to its section of the fuselage
So I'm just using a tiny piece of sandpaper and the tip of my finger. Making them out of softwood is coming in handy, as removing material is pretty easy.
I also found that rubbing the leg up and down while applying pressure makes slightly shiny spots that I can then sand.
It's a laborious but effective process
I've accepted that I'm not going to get it PERFECT. As long as the gaps are less than, like, 1/16 or 1/32 and can be arranged to be at the bottom where the leg will cover them, that's fine
Gap fill with wood glue mixed with sawdust. This will be sandable/stainable/paintable.
I was mostly being facetious. Clearly you are determined to achieve a higher level of quality. I wish you the best.
Never let perfection stand in the way of good.
That is the major struggle right now. I forced myself to accept them as-is and move onto gluing
Looks good enough to me and besides, you may decide to paint it with some paint that applies a relatively thick coat, which would end up filling those tiny gaps anyway. Anywho, keep going good work!