YLIXR
I have found that the best way to get a very polished user interface built and delivered is to prototype it as closely to the finished product as possible. Tools like Sketch and InVision Studio make this possible by having tools to rapidly apply animated links and transitions to screen designs.

Here is an example from Ylixr, an app and service I worked on a while ago. I recently revisited my work to refine my skills in prototype creation.