I have a deck that is grey and needs a powerwashing badly. What solution(s) should I use? Do I need to use a bleach/brightener as well? Will it kill my trees? Then I want a toner or oil stain...is Sherwin Williams or Pennofin the right ones? Also, what solution would be good to powerwash equiptment such as tractors? Could you use Dawn and water through the entrainment tube? Thanks.