I generally recommend the book Founding Sales (available for free online), but it's targeted at SaaS founders.

But you're actually doing something even more common: running a consulting business, and there's plenty of content on that for just that reason, so I would go find content on how to scale a consulting business, e.g. this seems like the start of a thread to pull on https://training.kalzumeus.com/newsletters/archive/consultin...

I wanted to say your insight about a consulting business is spot on.

I also recommend Founding Sales and think it would be worth the OP skimming.

Also, search for Steli Efti (founder of a CRM called Close) who has some great content for outbound sales. I thought he did a session for Y Combinator's Startup School but didn't just find it. But he has lots of great content and a bit of a hustle mentality.