Replying to my own post and probably no one is going to read this but...
the solution to over dimming Ozrunways (and not being able to get it back again ) while in IFR in bright sunlight, cloud etc is to put a white paint dot (eg whiteout typing paint ) on your iPad metal surround that is just adjacent to the brightness icon position, then if you cannot see the dimmed icon you place your finger just next to the paint dot and then move the slider to the right ( which you still can't see but it will be there )