Unfortunately, the work doesn't stop at just washing. Drying your makeup brushes properly is also an incredibly important step. The main reason being that you want to avoid water getting trapped between the bristles and the ferrule, which can both break down the glue holding the bristles and ferrule in place and cause mould to grow.
Both Martin and Young take a similar approach to drying their brushes. Young leaves them hanging over the edge of the sink so the bristles dry and excess water drips into the sink, avoiding water sitting in the ferrule, which might lead to a damp smell. Martin also leaves her set on a flat surface to dry fully, often overnight, as she says "there's nothing worse than having to pack damp brushes, which then risk losing their shape."
Although there are pretty standard ways to dry brushes, some people have taken some extremely creative measures to ensure their kit is dry and undamaged. On Facebook recently, I saw a person use a swimming pool noodle to create perfectly sized holes to hang their brushes from upside down. Committed to the cause is an understatement.