Jim: TWP (total wood preservative) is a outdoor above ground product. It was recommended from a quality independent paint store. I am not trying to sell it and will let you know what happens down the road. I told them I needed something that prevents decay, mildew and water damage allows moisture to come out of wood (allows drying) yet won't let water in. It needs to slow down wood from drying too quickly and can apply other oil type finishes over it. It does not leave a surface finish, it's a transparent penetrating stain, preservative. I got the "clear" color. . I indicated my timbers would be exposed for a while as I constructed bents to when I closed in building. Soft maple heart wood is prone to decay so I wanted something to protect it. I used a paint brush to apply to all surfaces and loaded my kerf cut on hidden side of timbers with it. I only put one coat on. One thing I can tell you is that you need good ventilation when you apply it as your eyes sure tear. I have some concerns of possible fumes while inside but figured I need the protection an have covered the TWP with linseed. They also said a large timber framer in area uses tons a watco urethane mix as a finish product some time after the structure closed in. I will put something on for my final finish.
I just fond this url on web http://www.coastalsealants.com/site/621476/product/1

Jim