If you follow our column, you know we regularly preach that 80 percent of a good paint job is preparation. Paint won't stick well when applied to a dirty wall, and doesn't look good when used to cover a damaged one. Once you've properly prepared a surface and begun painting, you'll want the job of brushing to be as simple and effective as possible.

Good paintbrushes are available in natural and synthetic bristles, and the use for which each type was designed is either marked on the brush package or somewhere on the brush itself. The message usually is specific - "for use with oil-base paints" or "for use with water-base paint." Generally, natural (animal hair) bristles are used with oil-base paints and synthetic bristles are used with water-base ones. There are some bristles designed to work with both types of paint. The brush package is important. Don't throw it away. It is designed to keep the bristles properly shaped.

In addition to selecting the proper bristle type, you should study the brush's overall construction carefully. Beyond bristles, better-quality brushes have several other important components: the handle, ferrule, divider plug and the metal insert.

The ferrule on a high-quality brush is attached with screws, rivets or brads. An indication that the brush is not as good is when the ferrule is the slip-on type. Nothing other than friction holds the ferrule in place. Imagine the friction-fit ferrule as a loose-fitting pair of pants without a belt. As easily as a loose pair of pants can drop to your ankles, so can a friction-fit ferrule slip off the handle of an inexpensive paintbrush. Here's a way to test the ferrule. Slap the side of the brush against the palm of your hand. If the ferrule is properly attached it will feel solid and won't wiggle. If the ferrule moves, buying the brush might be a mistake. If during the test several bristles fall out of the ferrule, put it back. There is no more irritating experience than trying to remove paintbrush bristles from a freshly painted surface.

An abundance of bristles also is important. This easily can be checked. By separating the bristles in half (in a line parallel with the width of the brush) the divider plug can be observed within the ferrule. In a good brush, the divider is smaller, leaving room for more bristles. In a cheaper brush, the divider is larger leaving less room for the bristles. A brush that has more bristles will hold more paint. This means fewer trips from the bucket to the surface being painted. Also, when there are more bristles to hold the paint, there is less chance that the paint will run down the bristles, onto the handle, and, ultimately, your hand.

Finally, it is wise to test the bristle memory. Part of what gives the painter the ability to paint straight edges is the shape of the brush. Good bristles have what is known as a memory, or the ability to flex back to their original position once bent or twisted in some other shape. Less expensive brushes don't have a good memory. To make the test, hold the paintbrush by its handle and with the other hand bend its bristles over at a right angle. If the brush is of good quality, the bristles will immediately spring back into place. A good paintbrush will retain its shape after many uses.

We aren't painting snobs. There are times when a cheap throwaway brush can be useful. However, we don't believe that such is ever the case when painting fine wood finishes and trim.

Once you are finished using a fine paintbrush, make sure to get it completely clean. Don't soak the brush in a can of solvent (water or thinner) overnight. The paint will settle to the bottom of the can and stick to the bristles, and the bristles might also be permanently bent.