For radiator pipe holes, I’ve used escutcheon plates with a dab of caulk behind them. Looks intentional, not like you slapped some putty on and called it a day.
That’s a smart move. I tried the “stuff some steel wool in and hope for the best” method under my kitchen sink last winter. It worked for a while, but then I found little bits of it pushed out onto the floor... so, yeah, not my proudest fix. Escutcheon plates with caulk sound way more legit.
On the door sweeps—totally agree about the rubber ones. Our place has these old, uneven floors and the fancier sweeps just leave gaps. The plain rubber strip is ugly but it actually keeps out the drafts (and whatever else might be trying to sneak in).
One weird trick I picked up from my neighbor: sprinkle a line of cinnamon near any tiny gaps you can’t seal right away. Supposedly ants and mice hate it? Not sure if it’s science or just old-school wisdom, but it smells better than mothballs at least.