Multi-Platform App Wireframing Using Sketch or other tools

I am looking for a wireframe designer with a proven track record who can help me create comprehensive wireframes for public and enterprise apps that span multiple platforms - mobile devices, web browsers, and desktop applications.

Key Responsibilities:
- Design detailed wireframes and prototypes for multi-platform applications.
- Utilize Sketch as the primary tool for designing wireframes.
- Follow Material Design Guidelines in the creation of wireframes.

Ideal Skills:
- Extensive experience with Sketch.
- Deep understanding of Material Design Guidelines.
- Demonstrable experience in designing for multiple platforms including mobile, web, and desktop apps.
- Excellent visual design skills with a strong portfolio.
- Ability to iterate designs and solutions efficiently and intelligently.