Low end soldering station tip quality...

[crispy_tofu]

nanofrog, are you really sure about the flux coating? I've had brass wool from Weller and Ersa (genuine stuff) and never noticed any 

I recall reading that somewhere.

Yes, Dave talks about having a flux coating on the wool in his Soldering Tutorial Part 1 (EEVBlog #180) at about 4:00.

[tooki]

I'm not even 100% sure that fully dried rosin does much as a flux.

What exactly do you think the core of rosin-core solder is made of, then?!? If it relied on solvents, solder would have an awfully short shelf life...

[KL27x]

I suppose so. The main active ingredients in flux are acids (abetic acid in rosin, IIRC), and I figured they would work better when dissolved in water/solvent. Maybe I was thinking about it all wrong.

[continuo]

FWIW: I've just opened up a brand new Weller "T0051384099" dry cleaning wool (brass) and it's definitely not flux covered. It's just plain metal wool, nothing more.