How to clean oil paint off brushes
If you used oil or nitro paints, the bristles must be washed with the appropriate solvent (synthetic or nitro). Once it has dissolved most of the paint, place the brush under running water with the bristles facing upwards: the flow of water removes the paint trapped between the bristles, but now diluted with solvent.
How to Clean Acrylic Paint Brushes
If you used water-based acrylic or wall paint, all you have to do is thoroughly wash the brushes under tap water (with the bristles pointing upwards) to eliminate any trace of paint.