Not a big fan of power washing to strip old finishes. Especially this time of the year. It will drive the water so deep into the wood fiber that it will not dry out properly before the stain needs to be applied. I always recommend 4-6 weeks of drying after a hard power washing. The wire brush is a big no-no! it will leave parts of the wire bristles in the wood and cause rust marks after the stain is applied. I would recommend dry media blasting like corn cob or glass then Osborne brushing. There is no additive that will stop carpenter bees completely. There is a product out there called NBS-30, but it cannot be used with water based stains (which I recommend on log homes) that will repel bees, but it does not kill them or stop them. Call Mike at 866-670-3020 for more help.