This thread could have easily been titled: "Looking for Tip Tips."
Glad you found a resolution. I never use abrasives on a tip because if it is cleaned/sanded/filed down to what I refer to as a tip's "quick", no amount of tinning will help past the next soldering session. As going into the "quick" will create a corrosion start and the cleaned/sanded/filed spot will harden and refuse to take solder properly down the road. Learned early on that filing or sanding a tip down to the "quick' ruins the tip.
I always make sure my tip is wet (cleaned & tinned with a bit a of fresh solder) when I set it down for more than a few minutes or am done with a session. I use a wet sponge only. I've found that using those metal scrub brushes tend to ware the tinning down to the "quick" faster than a sponge does.