Design an App Mockup

Hi, we are looking for someone with experience in graphics design as it relates to user interface for mobile applications. We would be able to provide very detailed wire frames (from a user engagement/app functionality point of view) - and would like you to work to refine the wire frame mock ups to conform to a very simplistic yet engaging user experience. Aspects of that would entail graphics, creating a color scheme, and working with our development team to iron out how to create the best user experience possible. After that process is completed - we would like to convert that to the graphical assets that would go into the actual development of the mobile application. We will start out with iOS, and transition into Android... maybe more after that. We're open to engaging a candidate in more of the phases of this depending on their time availability, etc. We'd like someone who is comfortable with the entire gamete of this process who is trustworthy and can work efficiently. If you can possibly show some examples of previous work that would be great as well. Thanks for your time and look forward to hearing from you.