If you own paintbrushes then it is absolutely necessary to know exactly how to clean them since it will make them last longer. Of course, this task is not pleasant and it requires some time so be patient.
Removing water-based paint from brushes
Once you are done using your brushes make sure you scrape as much paint as possible off of them. Then get either a bucket or a bowl, fill it with soapy water, dip your brushes in there and leave them for a couple of hours.
Once they are done soaking make sure you throw the water and refill the bucket or the bowl with the soapy water. Dip your brushes again and start removing the paint using your fingers.
Repeat this method as many times as needed in order to completely remove the paint.
Removing oil-based paint from brushes
Start with scraping as much paint as possible. Continue with filling a glass jar with white spirit and placing the brush inside. Leave it in there for a couple of hours so it can soak.
I recommend you remove the liquid and refill the jar a couple of times. Repeat this step until the brush is clean then rinse it with water.
And keep one thing in mind: Do NOT pour the leftover liquid in your sink.