If he's "flailing" then that means he's doing bad in the hand striking exchange.
You can't just teach him Wrestling, Muay Thai clinch work, etc. online and expects him to learn & apply it. Wang Chungs are usually horrible in the clinch, and I spar with WC's who do bang hard. Pure WC's don't like getting clinched, so being grappled is out of the question. I have videos of this but I'm not going to embarrass these WC's.
He's training in an MMA gym right now, so he will learn, but doubtfully, online. Right now he needs to work on what he's got and certain WC techniques do work against Muay Thai quite well, which is probably what he's going up against in his MMA gym. Just use your Wang Chung and expect to get hit a lot and lose a lot....but tweek it, by implementing what they teach with WC.