I've never had fogged windows in a MH, but many in my last house did. If the 'fog' is permanent, chances are it's the result of the trapped moisture etching the glass. If that's the case, there's only one fix: new window.
2000 40' Tiffin Allegro Bus \ 2002 Regal 2860 Commodore
1988 53 x 14 Skipperliner \ 1995 32' Party Cruiser
1984 Goldwing Aspencade \ 1976 Harley Sportster