Hi Alice,
Yes, firing your piece a 2nd will get it back to the "pickle white color" (the aura 22 may make some areas a mustardy yellow because its not burnished, but this is not a problem). Some of the Aura 22 will get absorbed into the fine silver during the 2nd firing, but this isn't a problem either. Just re-fire the piece at the regular firing schedule (1650 for 2 hours for PMC Standard). Then follow the directions on the Aura 22 insert, make sure they're the updated directions (you can download them from the PMC Guild's website at
http://www.pmcguild.com/gettingstarted/technicaldata.html). Some other people have come up with other methods for using Aura 22, but I've never experimented with them, the insert directions have always worked well for me.
If your Aura 22 is dry when it arrives just add a few drops of the media and stir with a needle tool (so you can save the gold, it will get absorbed into a toothpick). You want Aura 22 to have the same consistency as nail polish. If you think that you're Aura 22 is too thin you can always apply a 4th coat.
One thing to consider is that a shiny (polished) gold and silver surface do not look extremely different, especially when we're using fine silver instead of sterling. To really get the Aura 22 to "pop" you might want to use a slight LOS patina on the silver (LOS doesn't darken gold). Another option would be to do a matte/satin finish on the silver or gold and leave the other color bright and shiny.
Hope this helps!
Mollie