I like to wash my makeup brushes every 2 weeks. I feel like once I got older and developed adult acne, it would be better if I got into the habit of washing my brushes frequently. I knew that doing it weekly was not something I could do so I settled with doing it on a bi-weekly basis.
The way that I like to wash my brushes is to fill up the bathroom sink with water and let them soak as I clean them one by one. My foundation/powder brushes and sponges are always the dirtiest because they are the most used. I do have eyeshadow brushes but I use a dry makeup brush cleaner in between uses. That makes it less brushes for me to wash which is a definite plus.
I’m trying out the Beauty Blender Solid Cleaner in Unscented. I normally use baby shampoo but I ran out. So far I like it because it does a good job at cleaning my brushes.