Is this necessary / recommended ?

I wouldn't wax them. Painting or dying would be OK but probably not necessary.

Boil in baking soda to remove grease and what not. Also will make them not so shiny. Then just set them. Alot of people paint them witch works also. Still gotta get the factor oils off or the paint won't stick very well if at all.

I also am a fan of boiling them in baking soda and non chlorinated water then over floor the container with more water until it's clear .
If there brush or cedar tree's or anything like that where you plan on setting them you could add then to the pot for a second boil this can stain the snares and they can smell similar to the area your setting them in.
Allan

I spray painted some last year and I never removed any factory oil by boiling and they came out just fine.

ditto as Beav said.... i havent boiled cables for many years, not good for cables. Soaking cables in a diluted vinegar overnight one gallon vinegar to 4 gallons water and then put in baking soda solution to negate the vinegar, rinse, ready to go and cables have dull look.

I would never soak cables in vinegar.In only a few hours,it will completely remove all the galvanizing and will also dissolve any aluminum ferrules.
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This or Formula 1 in one thin coat. The paint should be more of a dusting than a coat. No need or desire to remove the little bit of oil that may be on them.

How does boiling them damage the cable?

It removes the oils from the inner strands of cable, within a couple months it will have begun to corrode (turns white) the cable from the inside out enough to effect their limberness, which effects their performance and speed. If you have a damp climate it will get worse faster, eventually the inner strands of the cable will begin to break and over time the little strands will begin to poke out and effect the locks sliding even to the point of, in extreme cases, the cables rusting and breaking completely. This could take as little as a year in salty/acidic environments, or a few years in dryer climates. As anyone who works with cable for a living, they will tell you for maximum performance never remove the oils from the inner strands of cable.

I do wax mine to prevent moisture from getting between the strands when in the ground.