In my experience, yeah that's basically it. If it helps to have an interactive demo to communicate things, keep it ugly when showing it to the client, and show them the final UI designs separately as static image files. Even if you've already done the work to bring the assets into the demo, avoid showing this to the client as long as is reasonably possible to manage their expectations because they will almost universally have a hard time separating the UI/UX functionality completeness from everything else.

Obviously there are situations where the client will, in fact, understand the distinction, but I assume they won't until proven otherwise.