I’ll probably regret writing this but Milo has never generated a hair ball. He produced a prodigious amount of frothy saliva last time he was in his carrier in the car, and he occasionally vomits up some food.
And he is very reluctant to have his tummy brushed. But I think that his habit of eating a small mouse regularly, bones, fur and all, scours out his system.
Our vet told my sister to let her Springer eat the bunny she had caught, for the same reason.