Hoya NDX400 filter

[meddyliol]

I am waiting for a Hoya NDX400 filter to arrive. I am a little concerned by reports of the coating coming off whilst cleaning. Apparently, the instructions that come with it say NOT to use cleaning fluid but the Hoya website say to use fluid. I am a little confused (more than usual). I have some Baader Optical Wonder Fluid and was wondering if this would be OK to use. If anyone has one of these filters I would really appreciate some feedback. As a matter of interest as one of the main uses of this filter is for water and water drops on the filter are part of the problem, what about putting the filter on the lens first, then a UV or clear filter on the outside? That would protect the filter and have no effect on pictures.

Thanks

Brian