Mine are all short haired so don't need brushing, although in the past I had a short haired male who's back legs got very knotty and I'd just use a soft bristled brush to tease out the knots
If they're moulting badly I do use a furminator on them though along with plucking out loose fur with my fingers
But yeah if they're short haired and don't tend to get knotty they don't need brushing unless they're going through moult and even then a lot of the products sold in pet shops aren't very good