Pressure washing is a vital part of prep work prior to exterior staining. This process removes any dirt and helps bring the wood back to its original look. When pressure washing it is important to use a wood cleaner/brightener to help draw out the dirt and old stain from the wood. Not all old stain will be removed but doing this will give the best possible results. Once the wood has had time to dry out (usually overnight) a stain coat will be applied. We always recommend an oil based stain for exterior applications. Oil soaks deeper into the wood than water based stain, thus giving a deeper, richer look. ALWAYS read the manufacturers instructions on the can, most of them will recommend 1-coat, some call for 2. DO NOT apply more coats than they recommend. Doing this will not allow the additional coats to dry properly resulting in a sticky, uncured mess. We have had to help a few homeowners out and remove the stain they spent all weekend applying because they did too many coats thinking it would last longer.