"Sole proprietors can’t pay themselves wages."

Because all of it is theirs, already. They are not a cost to their own business.

"It's registered as an LlC."

You mean LLC?

Have you considered Safe Harbor for estimates? See this article:

https://turbotax.intuit.com/tax-tips/small-business-taxes/estimated-taxes-how-to-determine-what-to-p...

That's what I rely on when a client has a constantly changing taxable income, and it's especially useful when they are on a constant increase. You just have to explain the difference between Safe Harbor and actually having paid in enough in estimate payments that they will hardly owe a balance, or at the least, they intend to be prepared if there is a large balance due (but at least they are not subject to penalty and interest).