Agree with all for once. Once you get all the crud off, you have to tin the remaining contact areas without melting the cabinet. Yes you can scrape and solder the ends of springs, and pull them out a bit, and roast a bit of copper braid on the minus side if you are careful. You can always try again, but don't harm the cabinet.

wonder if this will work for battery terminals
http://www.home-jewelry-business-succes ... welry.html
never tried it myself