I've done it the non pressure way, only 1x though & had to stop after doing the garage (with dormers). The H/O told me I couldn't use his water so I had to pull the plug. I also did 1 the traditional way (lift & pressure washer) with another company, a bit more labor intensive and the supplies are more expensive.
The person (I'm sure we all know who) that explained the non pressure process asked that I not publicly share his method, but it's similar to asphalt shingles with a few slight differences. If you'd like give me a call and we'll discuss.
The traditional way (3 step process), is what I'll be marketing next season and I think it's the more professional of the two. Start by applying a sodium perc, clean with low pressure, then neutralize. I was shocked at how slippery the wood gets and almost slid off a 3/12 one story roof, so you'll need a lift. I've never done it before, but you might want to seal at the end.