I need to restain the case around a hot tub and the deck that surrounds the hot tub outside. I think the deck is easy enough. Just use some sort of deck brightner and cleaner and stain it since it has never been stained before. I don't want to use a pressure washer because I am afraid it will rough up the wood. The hot tub case is weathered and has some grey colored looking areas. It is redwood. Do I have to strip the old stain off the redwood before I stain it again? Is it best to use an oil stain versus a water based stain?

Ready Seal. Its the best

i would sand it first.