Describe the real sticking point
If the chorus is weak, the bridge is not working, or the song feels flat, say that directly.
Rough is fine
Rough demos are often enough. Waiting until everything is polished can slow down the useful part.
Separate goals from references
Reference songs help, but they work best when paired with a clear explanation of what you want to change.
Keep the first message practical
Project type, timeline, links, and the real problem are usually enough to start the conversation well.