A picture is worth a thousand words. So when it comes to showing your users what the application is going to look like Balsamiq Mockups https://balsamiq.com/ is hard to beat. I love the desktop app. It’s easy to learn and use, you can easily add your own sketches and it beats using a white board. The results are somewhere between that pencil sketch you did on a napkin and hiring a professional graphics artist.
The truly professional end result can be presented directly through the application or you can easily copy and paste them into your Word or PowerPoint presentation. No more photographing the meeting whiteboard or scanning your pencil drawing. There are even online video tutorials so there is no excuse not to give it a try.