As you paint, you will become increasingly familiar with the way the brushes handle the paint and what they can accomplish for you. Pretty soon the paintbrush will become a part of you that you intuitively know how to maneuver.
Paintbrushes for acrylics and oil come in many different shapes and sizes. The shapes and sizes of the brushes you choose to work with will depend mainly on how large you want to work, and how detailed you want to get. Take a look:
There are 8 main types of artist paint brushes that are used with acrylics and oil, shown above. Each one is specially intended for different uses. Details in Artist paint brushes.