Cedar siding question

We have cedar siding on our 2 year old house. After the siding was
installed, we sprayed it with TWP stain. We used the Honeytone color
which we were warned had the least amount of pigment and uv
protection. After two years we are noticing some light greying on the
bottom boards on the two sides that receive the most sun. We want to
clean that off and have been told by TWP to use their cedar cleaner
which they said is similar to a deck wash(I presume that it has some
acid and clorine in it). TWP suggested we use a pump sprayer to apply
the cleaner and to saturate the boards we want to clean and, after 10
minutes, lightly pressure wash the boards to remove the cleaner. They
say that the boards will be restored and, after waiting a couple of
days, we can reapply the TWP. They also told us that, if the other
boards that haven't greyed will absorb water(using a hose) we can go
ahead and apply more TWP to those areas.

I would appreciate any comments about this process from people who
have dealt with this kind of siding and stain and the kind of
situation I have experienced. I am especially interested in
experience with the greying issue and how to remove it. If pressure
washing is involved, I need to buy a pressure washer and would
appreciate recommendations and suggestions about the pressure to use.

Thanks for any help.