10-4. Power washing is cancer to a log home. The only time we use a power washer is to rinse a hand applied soapy mixture from the logswhen washing before a maintenance coat of clear is applied. We are standing back 15-20 feet so that it is only a light mist. Any kind of power washing with the wand up close to the wood (which it sounds like you are going to have to do to be able to remove any old finish)will drive the water so deep into the wood fiber it will never dry out properly. If you still power wash, you should allow it to dry for at least a month of good dry weather (plenty of time for dirt and mold to settle back on the wood).