You could try anything you want, it may work, or have really bad results. My opinion,
You need a picture for us to give you better guesses, or what you really need is a professional.
Sometimes ventilation could cause more issues. Try a guy named Jeff May (google him)in your area. His company does house diagnostics and solutions.
You may need to go with different types of insulation, or even a separate roof over your existing roof.
There are no easy answers, all homes are different.
Tell us how you make out.