Homebrew PCBs

I have always found using 1000 or 1500 sandpaper (get some 'adhesive 
foam sheet' from the craft section to make it easier to use by hand) 
to rough/clean the copper works much better than scotchbrite. Whenever 
I see 'use a scotchbrite pad', it always makes me wonder, just WHICH 
one they mean? There's at least a dozen different types/styles/grits.

After that, I clean it off with 91% Isopropyl alcohol which you can 
find in wal-mart or drugstores. It doesn't have MEK or methanol since 
it's already toxic on ingestion (but is safe for skin). Also, check to 
see if your paper towels are leaving a film as well. I was using Scott 
shop rags (the white ones) from Home Depot with acetone before, but 
they seem to leave residue on the metal. Using the isopropyl with 
regular Bounty or the one for window cleaning seems to make the metal 
much cleaner.