Lethal Lashes Shampoo. 
Make sure each client comes in with squeaky clean lashes within the hour of seeing you OR they clean their lashes right before you start. Have them clean their lashes at least every 2 to 3 days at home. 
Clean GENTLY and make sure to concentrate on the lid and lash line.
Sell the shampoo to the client as well! Remind them that a little goes a long way!