Reddit mentions of Extra Thin Fiberglass Scratch Brush | BRS-290.00

You can try doorbell wire at hardware store, if you can find 22-24 gauge that would be ideal. That’s what I used in the past, still works. The trick is scraping off the coating on the circuit board. For that I use a fiberglass scratch brush..with a little flux and some heat (not too much or you risk the trace lifting) and you can repair the circuit.
I have tried using a trace repair pen on a Nintendo DS and it worked, but didn’t work on the Xbox.

Better to use one of these

Since everyone caught the leaded vs non-leaded error I won't even mention it.
However, I'm just gonna nip one thing I did catch in my read-through right now:

> Fast drying WD40 can also be somewhat useful for cleaning PCB’s.

I really hope you're referring to WD's line of electrical contact cleaner here, and not plain ol' WD-40 lubricant. Should probably make that a bit more clear so newcomers don't assume you're referring to plain WD-40.
Do not ever put standard WD-40 on your PCBs or components, it is oil-based and can eat plastic and rubber components if left to sit.

To add in/on/around:

• Craft knife works for cutting traces wonderfully. However, my favorite scraping tool ever for exposing a trace for soldering is a decent fiberglass pen/scratch brush (like this one), does the job fast and clean, and generally easy cleanup. Just be gentle when scraping.
  
• Q-Tips are cheap and do the job well, but if you want to be 100% clean go for some lint-free swabs and wipes when you clean up your PCB and joints.
  
  Fantastic little batch of starter info here, though it could use some formatting work. Mods, pls sticky/pin this.