Yeah this is great. The sanding trick should solve your corner issues.
You are probably all set on sanding technique and equipment [1] but if not… I’d probably start mechanically like with a Dremel or even better a belt sander to rough it out, then use a nice sanding block to get the final shape and surface dialed in.
If you never saw this post, my favorite type of sandpaper and block are these guys:
after all you’re @pubultrastar! The pubultrastar. ↩︎