WLONG,
The easiest and fastest way I know of is to boil them in Drano Lye Crystals.
Get a big black enamel corn pot, or a cut off barrel, build a fire under it, when it boils, put in your traps, still boiling, pour in Drano, boil for a minute, remove and rinse with a hose, don't touch with bare hands, hang up to dry and air out for a couple days before dying and dipping in wax.
The Drano will remove the rust and any other contaminants that may be on the trap.
Good Luck
CoyoteJW