My kid wants to use my dad's vintage US Divers circa 1970's black scuba
fins in the pool but I won't let him until we solve the problem of the oily
rubber coming off in our hands.

We bought new straps and soaked the fins themselves for days in a bucket of
pool water, but still the oily black inky rubber comes off as you rub the
fins in your hands.

Is there a "coating" or some way to stop old scuba fins from smearing oily
black rubber on everything it touches?