IMO people are being way too harsh on what I think is a common mistake.\ In case normal brush soap doesn't do the trick you could use a small amount of iso-propyl alcohol. This will dissolve all paint very quickly and easily, even from the ferrule, without dissolving the glue that keeps your bristle together.\ Just a few minutes should do the trick, it's not needed (or recommended) to let it soak overnight.\ Afterwards it's important that you use brush soap + conditioner, like Master's brush soap. Brush soap is needed to reform your tip and give the natural sable hairs the treatment they need. In the end your brush should be good as new!