It should brighten up fine just with a 30 second dip in activator. just make sure it doesn't start fizzing. If it does then you have gone through the copper back to zinc in the pot metal.
Process should be de-grease, rinse (hot tap water will do) then activate then distilled water rinse and straight into the nickel tank.
copper will brighten up in seconds when it is dipped in activator.
PS just email me the pic at
mark.smith5@baesystems.com, will be quicker
Cheers
Mark