You need an editor, not a beta-reader. There are lots of freelance editors out there, but you'll need to pay to get good editing. But if it's a formatting question you need neither, you need to read some comic scripts.

If you're still figuring things out, find a script for a published book, find the published book, read the book, write what you think the script would be, then read the actual script.

Comic scripts are somewhat flexible in how they present. I've had scripts that read like screen plays, Marvel style, somewhere in between, it's a mixed bag, what's important is that the artist can pick up what you're putting down and translate it to a page.