Funny how sometimes certain things are exactly perfect. Did you know that the blue Pentel 0.7mm mechanical pencil (sometimes it’s marketed as for “engineering” now I know another reason why…) is the exact size of the inner diameter of a PCB thru-hole?
I used this technique to clean out a few thru-holes that I had soldered. Not sure how you’re supposed to remove solder from a previously-soldered thru-hole, but this worked surprisingly well given it is exactly the correct size.