Doubleset, I assume that gunk is just froth left from the vinegar attacking the rusty metal. It isn't wax. My solution looked identical after cleaning a dozen of rusty coil springs that had no wax on them.
When traps get as rusty as those pictured there isn't any wax left on them. Boiling is the best way that I know of to remove old wax in the trap preparation process - dyeing and waxing.
Shown below are before and after close-up examples from my rust removal project last year. I bought the traps used, and they had been hanging in an open shed for 20 years according to the seller. Surprisingly, as rusty as these traps were, they cleaned up exceptionally well after a 2-3 day soaking.
I did not have to wire brush them - just ran some coarse steel wool over them to get the residue chunks off. They were rinsed with fresh water and left out to get a thin film of rust prior to dyeing and waxing.