Liquid silver ("Leitsilber") works quite well, but you have to keep it mixed or you'll have too few silver particles on the traces (had to learn that the hard way). Also use plenty of liquid silver and paint the trace as thin as possible with a very thin brush or a toothpick.
I've repaired a few MS Natural Keyboards (damaged by Coke spills) that way (they don't make the Elite any more) and they all still work after quite a few years.
