Brillo pad and lighter fluid
It's just a solid resin ball. Any good bowling-ball specific cleaner should do nicely.
Brunswick has their own Remove-All;
Track has a great deep cleaner in Clean and Dull;
Ultimate Bowling products has an excellent one in Black Magic Rejuvenator; Legends ball cleaner is very good,
as is Neo-Tac's Liquid Nitro.
Some people to be cheap use mixtures of household cleaners. Be very cautious about that. I'm not saying don't use them; I'm simply warning you that anything can happen SOLELY because they were not designed to clean bowling balls.
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Bowling: Just like hand grenades and horse shoes, you only have to get close.Life: Deal with what is.