Don't submerge your brushes, and don't use hot water.
This lesson I learned from the comments section in several of the videos where users left their brushes to soak: Hot water can cause the glue to loosen on the bristles and cause them to fall out., so any hacks offering this advice I'd reconsider.
And the winner is…
Plain dish soap and water was the best method for cleaning my makeup brushes by far. Depending on how dirty your brushes are, you might need to go several rounds gently swirling your brushes around a cleaning mitt or mat, but the effort is minimal and so is the cost. It's a gentle method and doesn't risk ruining your brushes.
After cleaning them, don't forget to properly dry them so you can keep them in tip-top shape. Loiz advises squeezing the excess water out of the bristles with a dry paper towel. "Then, I lay them flat to dry overnight on clean paper towels. After they're dry, I store them upright in cylinder containers," she said.
While I don't wear makeup that often, this served as an important reminder that washing makeup brushes don't need to be an intensive, dreaded chore. Just a few squirts of dish soap and some water will do the trick to keep them clean and looking as good as new.