Brushes are the artist's main tool for applying paint and are available in an enormous array of shapes and sizes. Choosing the right brush for the job is vital for good results. Since they vary greatly in cost and versatility, you must choose wisely. It all depends on the techniques and effects you wish to achieve.
Every type of brush is suited to a task that will leave an individual mark. To begin with you don't need a huge variety, start with three or four that will satisfy your initial needs. Brushes for oil painting are generally of two types: Stiff bristles or soft hairs. Bristles are made of hog's hair and are good for establishing the initial stages of composition and laying in large amounts of colour, particularly if your painting is large. They are ideal for impasto work. Soft hair brushes made from real hair and sometimes synthetic are useful for smooth finishes and softer lines. Bristle brushes encourage you to work loosely giving life and texture and a feeling of vigour. They are stiff and hard-wearing. Each strand of a bristle brush has split ends that hold large quantities of paint useful for bold decisive strokes. Look for ones that keep their shape and have plenty of spring. Avoid synthetic substitutes which are made of nylon and loose their shape rapidly. Bristle brushes are also available in a variety of shapes. FLATS are versatile and essential. They have flat ends and long bristles that hold a lot of paint. Ideal for applying broad rectangular strokes and areas of thick bold colour as well as short dabs. The side can also be used to create thinner lines for more detail. They are useful for blending and working up to an edge. BRIGHTS or sometimes called short flats are the same shape as flats but with shorter bristles. These brushes dig deep into paint and leave strongly textured marks. They are useful in applying thick paint to create impasto effects. Because of their shorter bristles they are perhaps easier to control making them better for moving in on details. ROUNDS have long thin bristles that curve inwards at the ends. They are good for the technique of glazing and for more delicate lines and thinner lines. They are useful for sketching in the initial compostion. FILBERTS are similar to flats but have a flat ferrule curve inwards at the end. They are also available with both longer and shorter bristles. They make soft tapered strokes ideal for applying short dabs of colour.
Decorator's brushes can also come in handy, generally they are cheap and hard wearing. You can load them with an enormous amount of paint to heavily cover a large area. They are also usefull in preparing a board quickly and evenly in undercoat and base colour.
Each brush type is made in a variety of sizes with the smallest 00 up to larger size 12. Which type and size you select will depend on what you want to achieve.
Tip: before boldly applying paint to the canvas with a new brush you are not familiar with, first test the strokes it makes on a clean sheet of paper or discarded canvas.