Alan
I've had some problems with QHY9M dewing mainly due to accidentally unscrewing the front glass due to tight threads and exposing the inners the the outside air. What I do is get a very large thick clear zip lock bag and put the camera inside along with the front glass and a fresh 500g bag of desiccant. Zip it up and leave it for 48 hours to absorb all the moisture. Then I carefully screw the front glass on whilst it is still inside the bag. It always works. The desiccant can be easily found on Ebay like this one..
http://www.ebay.com.au/itm/4x-500-gm...7420350&_uhb=1
To refresh it simply put it in the oven at 120C for about 2-3 hours and put it in the bag whilst still warm.
Cheers
Stephen