That evidence comes in the form of (1) seeing other scientists who utilize artists to get funding or publicity about their work or (2) finding themselves getting excited about research after seeing some kind of art.
And as I continue to work on the piece, I like to involve the client in my work, so I send work in progress images along the way.
Just like any lab-based skill, artistic skill takes time and effort to master, but a simple workshop can really open eyes as to just how many different types of skill you need to do science art well!
If you someone who doesn’t have the skill yet but has lots of connections to scientists, science communicators, etc, then you need to take time to build your skill while sharing your progress with your great connections.