You could try this:
http://www.bavaria-direct.co.za/models/faq.htm
How to strip the enamel coating off copper wire
Burn off the coating with a cigarette lighter or better still, a pencil torch. A heatsink will help avoid burning the wire back too far. It's like a thin alluminium clothes peg. Electronic supply stores may still have theml.
Burn the wires about 1cm back. Hold the bunch of wires flat over the edge of a table and rub with an ink rubber (eraser) to remove most of the remaining carbonated coating.
Use Bakers Fluid (from a hardware store, for soldering galv gutters etc,) on a cotton ear bud. This rips off any oxide when heated with a dry soldering iron tip.
Tin with solder.