Cleaning a wood deck prior to staining is the best chance of getting professional like results. Dirt, mold, mildew, wood graying and any remnants of old failing stain needs to be removed. Getting a deck back down to bare wood will help guarantee proper stain performance and help you get the most out of your deck care. Wood fibers are delicate and can be damaged easily. The most common way a deck is damaged is by excessive pressure from a pressure washer. This can leave lap marks, splinters, and raised grain (fuzzing).
Sometimes during the wash process wood takes a beating. Strong chemicals, strippers and high pressure can all take its toll. In order to remove an old failing stain you might have to use a strong mix of cleaner or stripper. Perhaps you got too close to the wood while washing and furred it up in some areas. If cleaner or stripper raises the grain of the wood and furs up the deck it is not the end of the world.
Light sanding the deck will rid it of the furred wood grain. Buy or rent a floor buffing machine and perform a light sanding with a "Sanding Pad" in the fuzzy areas. Once you knock the raised wood grain back down you should clean the debris off the deck prior to staining. A leaf blower or broom can be sufficient. If you did a lot of sanding and there is dust everywhere you may have to rinse the deck with water and let it dry again before applying stain.
To reduce the chances of raised wood grain try not to mix the cleaners stronger than necessary to do the job. Do not let the cleaners dry on the wood prior to rinsing. Be sure to brighten (step two of RAD kit) while the deck is still wet after washing. If the deck dries prior to brightening it could raise the wood grain creating this fuzzy appearance. Try to use 800 psi to wash the wood. If you do not have access to a nozzle that will put out 800 psi and have to wash with high pressure be sure to hold the tip of the gun at least 12-18” away from the wood while washing.