Author here. Happy to answer any questions about the post or about my experience at Google.
His career trajectory has been similar to your story, in that he was a line engineer who went independent. The think that makes patrick great, though, is that he took the time to write up all his lessons in a blog that is essentially a how-to guide for engineers who want to make the move from "I just write code" to "I am a sucessful self-employed software consultant.
If you haven't come across him before, I strongly suggest you check it out