You’re also going to need some liquid soap—I use regular hand soap most of the time, but I’ve also used Mona Lisa Pink Soap in the past and they both work well. The Pink Soap has some bristle conditioner mixed in, so it may prolong the life of your brushes better than regular hand soap.
 
Of course, you won’t need the thinner or soap until you get all the excess paint out of your brushes. Here’s where a little finger strength comes in handy. Take your brush with one hand and a piece of newspaper with the other, wrapping the newspaper around the metal part of the brush.
 
Then, just squeeze as tightly as possible, starting right at the base of the bristles, while pulling the brush back through your fingers. Get as much paint as you can out of the brush.
 
Go ahead and do it a few times, and especially try to remove all the paint that’s stuck close to the ferrule (the metal part of the brush.)
 
You should end up with splotches of paint all over your newspaper and a lot less of the paint left in your brush.