Scott,just take a wire brush to your traps.That should remove the surface rust.
When I used to dye my traps(I cold dip now),I would place my dye in the water and bring it to a near boil.I would then turn it down to a simmer and place my traps in it.After a few hours,I would remove my traps.Other times I would bring the dye water to a boil,turn off the fire and leave my traps in the pot over night.
Tom