I use Ozrunways - that is I use the simple parts of it I can understand. The fuel and flight planning and anything outside range and bearing, ETA, ETE and suchlike I can't use because I can't seem to audit on screen and satisfy myself that the numbers are correct.
This is a common problem with applications : its called "featureitis" - more and more functionality gets crammed into the App - making it too complex for mere mortals who are not "power users" in computer parlance.
One of the cures is to find some simple pilots who have not yet been exposed to the App and get them to write a manual from scratch.
This is why some japanese factory car maintenance and repair manuals are so good - the factory literally makes their engineering apprentices write it.