Protective Substance 
If brush's hair is fixed by a protective substance then, before using the brush, put it into a glass of water with a temperature less than 50 C (122 F) for 5-10 minutes. After that rinse it out in clean water. 
  

After-Painting Care 
After painting, rinse a brush thoroughly trying to remove all the paint left. Use an appropriate solvent:

Keeping The Hair Shape

• Don't leave brush's hair in the contact with a bottom of the glass with a solvent even for a short time. Hair might lose its shape forever. Use a glass with a special brush's holder to prevent the hair from contact with the walls and the bottom of the glass.
• Hair of a dry brush could also lose its shape. Keep a brush horizontally or on the handle (hair up).
• If you use acrylic paints rinse a brush in the water immediately after using it. That is if you use many brushes all the brushes except one (which is in use) should be kept in the water. Acrylic paints dry out fast especially near a ferrule and they are difficult to remove afterwards.
• Sometimes if hair lost its shape you might somewhat recover the shape by putting a brush into the water with the temperature 80-90 C (176-194 F) for 2-3 minutes.

The Other Recommendations

• Don't press on a brush while picking up a paint, painting or rinsing the brush (especially, if it has a soft hair).
• Always rinse a brush in the water after using a solvent.
• If you don't use a brush for a long time keep it in a closed box.