Generally, I use Illustrator or Sketch for responsive comps, but with the latest updates to Adobe CC, there's something you could look into to make your life easier. If you have an iPhone or iPad, this might be something worth trying:
https://helpx.adobe.com/mobile-apps/how-to/app-prototyping-photoshop-preview.html
Personally, I use an Android device, but I do use CC. There are many different ways to approach creating responsive comps. You can use Illustrator, Photoshop, Sketch, whatever you feel comfortable working in. Search Dribbble for free wireframe and responsive device kits (vector or PSD) – or search around the web for free wireframe kits. There are tons of freebies that can help get you moving in the right direction!
Adding to what Darth_Vader said, try to include a grid overlay as a guide, and stick to few layouts. The most you'll probably ever need: desktop, tablet and phone. From there, a designerdeveloper who knows responsive design will get the idea.
Lastly, be sure to check out UXPin for their free ebooks. They have a lot of great information on designing UI and creating wireframes/mockups.