Man... I really enjoy using this software. It's really intuitive and just a lot of fun playing around, and on the plus side, building a huge library of assets for either Unity 5 or for the Unreal Engine.
Best way to learn Grand Designer, is just by playing around with the sliders, but it always comes in handy to watch Ignishot's Grand Designer YouTube tutorials. Just give it a go and have fun with it. I sure do... Yahoo !!!