I wouldn't think the foam part of the ensolite would harbor mildew as long as the vinyl side is intact and the ensolite is glued well to the fiberglass.
Cleaning mildew off the vinyl surface should be enough.
The problem I have with all this is the strong chlorine odor that comes from anything I've tried so far about does me in. How was the Tilex in that regard?
What I've found best so far is a small paint
pad for most of the scrubbing. It still allows solution to run down the handle and down your arm, but less so than a brush.
If you've found a method that works well, let us all know.