The set comes with a 2-inch flat brush, a 4-inch flat brush, and a round brush. The drill isn’t included, but you can grab a basic Black and Decker one ($29.99 on Amazon) that’ll do the trick.
Promising review: “I thought my hard water stains would never come off my shower doors, but I bought this awesome brush set, and it’s amazing! I’ve tried all the hacks — drier sheets, clean erasers, lemon, vinegar — nothing works like this brush! I used Zep shower cleaner with it! In the picture, the side on the right is the part of the door I cleaned, and I still have to clean the left side.” —Traci D.
Get it from Amazon for $18.95 (available in six colors and stiffness levels).