If you are using them to trap dogs----(coyotes and fox) I do not like using wax it will hold smell. I use a product called speed dip, made for trappers. It dyes the trap, penetrates the steel for protection, and will last 2-3 years. It is a cold dip and will not affect the springs like boiling will. It comes in black, brown and white, I mix brown and black for dirt trapping. The traps have to rusted for the dip to penetrate the steel. If they are real bad just take a steel brush to them. I have used it for more than 15 years.

Get a 5 gallon bucket (or larger), and fill it halfway with wood chips. You can usually find a place where a chip truck dropped a pile or a sawmill would give you plenty. Put the traps in and fill it with water. Leave it all in the bucket for a couple of months. I dont remember what exactly eats the rust off, but it works and also dyes the traps a nice dark color.

If you have access to a tree covered bog, you can bury them in the black muck - works the same way.

You need the traps to take on a light coat of rust to absorb the logwood crystal/powder dye. Taking them back to a shiny condition will prevent the traps from blending in with the surroundings and also will absorb more odors than a dyed trap. Be careful with Speed dip since it uses a petroleum-based thinner to apply and they WILL need to air out for some time.

Surface rust like many said, use a wire brush and take off that off but not to a shine.

Long fur (coyotes, fox, cats) will respond better to good dyed traps and careful placement (sound/secure) of the trap, than a shiny one which can emit new metal odors. You don't want to alert the species to anyting other than the bait, lure or urine you use as an attractant or a dirt hole or scnet post.

Good Luck!