lather, rinse, repeat

From the directions on a bottle of shampoo.

lather, rinse, repeat

1. (informal, often humorous) Indicating that an action or process was repeated, or needs to be repeated.
   • 2005, Deke McClelland, Galen Fott, Photoshop Elements 3 for Dummies

     Use the step backward icon again and experiment with the other three icons, drawing overlapping shapes. Lather, rinse, repeat.

   • 2006, Annalee Newitz, Charlie Anders, She's such a geek!: women write about science, technology and other nerdy stuff

     Then, burned-out after a spring and summer of machining, testing, tweaking, lather, rinse, repeat, I took a driving vacation with my husband […]

   • 2007, M P Dunleavey, Money Can Buy Happiness: How to Spend to Get the Life You Want

     Lather, rinse, repeat until you get tired of watching your money go down the drain.

• the mixture as before