[sdiy] solder beads?! 8^p

[Nathan Reeves]

hello all, i am about to solder on a replacement clip for the memory  
battery onto a PCB but the solder on my iron is not working right?!?!
do bits (tips) go bad?
i tried to clean off with steel wool brush, but still the solder/flux  
beads up and i cannot even tin the tip!  any ideas?  i thought dirt  
was the culprit but not sure how to get it any more clean, maybe run  
in the dishwasher?!

what is a good size tip for a weller spg40 to do PCB solder work?
cheers
nate