With the exception of a hot air rework tool, a soldering iron should complete a nice fillet within 3 seconds. Adjustable temperature kits tend to hide the skills needed to work with the thermal mass of the iron itself.
Brass wool is often just copper plated steel, and will damage the plating. Thus, pin holes in the tips iron, nickel, or chrome plating begin to pit the copper core.
That's certainly a concern, but it's completely ameliorated by buying real brass wool.
The stuff that came with my (apparently genuine) Hakko 599B is non-ferrous (and is therefore not steel). Refills are Hakko part 599-029.
Soldering iron tips are usually made from copper with a thick iron plating. On Moh's hardness scale, iron doesn't care much about what brass thinks. :)
Yes I've only used the one that came with my Hakko soldering iron, and I just got a replacement from Hakko since my old one is getting pretty full of solder bits.
The tip on my soldering iron is perfectly fine though.
Was never a fan of spendy rapid PID based mini-heaters, but some people do prefer that design.
In situations where PCB ground pours removed thermal-reliefs for power handling reasons, mini-cartridge-heaters often simply don't have enough thermal mass to heat an area fast enough without the control-loop missing temperature ranges and or time limits.
Anecdotally, same reason good portable butane catalytic iron units are often superior to USB-C/battery operated units.
Note Zinc contact is restricted in some places, and that ban includes zinc-brass sources. Best of luck =3