Revlon Colorstay foundation problem?

okay so I found the best way for me to apply the CS foundation is by using a stippling brush. But now it's reallyyyy hard to get the foundation completely off of my brush ...wait, let me rephrase that, it's IMPOSSIBLE to get the foundation off of my brush. I use a gentle facial cleanser to clean my brushes and it used to work with my other foundations but it doesn't work with this one. Suggestions?