A friend of mine worked at a public airline and whenever they had a bad quarter, things like coffee would get cut so people would feel it. But those types of industries operate on razor thin margins.
I was an engineer as well early in my career. As an entrepreneur now, I've been doing sales for the last 8 years. I've never been formally in any sales role prior to running my own business, so I mostly learned on the job and on my own through trial and error.
I think when most people hear the word sales, it usually has an adverse reaction. Someone mentioned here that being a consultant is a good way to approach it and I've found that to be true.
I've recently heard of a great acronym that helps you think of how to approach sales:
S - Serve - go in w/ a service mindset
A - Ask questions - don't go yapping about your offerings just yet. Find out what their pain point is. This way you know what to offer and what to skip
L - Listen intently. I think a lot of times, I'm very guilty of "waiting to speak" vs listening.
E - Emphathize - with the customer and their pain. This is why they are coming to you.
S - Summarize in your own words what you heard.