I actually take very good care of my brushes and always have done. I have a great mix of brushes expensive and inexpensive - As I have said before I don't just buy products because of the brand name - I buy them because they are good products.
Firstly - I wash my foundation brushes after every single use. I wash the rest of my brushes after every few uses - Although I do try to keep a certain brush for dark eyeshadow and a different one for light eyeshadow etc - that helps to prevent a mix of colours.
I mainly use this MAC Brush Cleanser - Its about €15 or so and it lasts a good while. It cleans the brushes so well and leaves them nice and shiny. However every now and then I use a make up remover to clean them - a change is as good as a rest.
I recently bought this ELF Brush Shampoo from the ELF website -It was only €4 so its good value. I used it today for the first time and I must admit I was very impressed! I will be using this one for good when the MAC one runs out.
Here are the brushes that need cleaning - I have all different makes of brushes as you can see. In order to clean then I lay them out on a piece of kitchen roll. Then one brush at a time I dampen the bristles only with lukewarm water. I am very careful to only wet the bristles as if water gets into the handle of the brush it can damage the glue that holds it all together and then you end up loosing the hairs :( which is not a good look.
I then dry the brushes with a piece of kitchen roll and leave them on the window sill to dry in the beaming sun.
Make sure to reshape the brushes and hey presto - Lovely and clean, ready to be used again :)