You can pressure wash the interior of a trailer sailor -- I did it last year to my Catalina 22. Took everything out I could, and hit it with the foam cannon attachment. Then some elbow grease on the stubborn spots. Once it was decent, I went to town with the pressure washer (within reason). Cleaned my "bilge" and everything else. Of course it was in my yard and I had 2 pumps placed in strategic spots to help empty the water. Then a lot of drying with everything open, and a fan helping to move air through the boat. Not ideal, but it was getting to the point where it really needed a good deep clean.