I’ve probably said this before, but when I get stuck trying to visualize something, I go out to Pixabay or simply google whatever it is to find some pictures. It can really help me describe something when I’m having difficulty finding the right words. If you can’t see it in your mind when you describe it, the reader probably won’t, either.
Having a visual “story board” fits well with this. Grab some pictures of your characters as well as various scenes from your story. This is especially helpful if you tend to write primarily action and dialog. They’re important, of course, but imagery is important to make the story really come alive. Otherwise, it may wind up reading like a screen play, which really doesn’t establish a bond with reader like visual and emotional details.