I've published 4 books (Wiley) and sold around 100,000 copies total. There is a reason why publishers ask you for your sales and marketing plan for your book before they publish it... you have to have a platform to sell to. A built in audience.

It is almost impossible to sell any copies of a book from someone that doesn't have a following, let alone make a living from it.

There is no quick fix/tool. You need to create a following/audience based on your subject expertise. I'm not talking about a Twitter following, but a reading following. Do you currently have a site/blog? You need a way to capture readers email addresses and build and nurture that list. If you don't you can use a place like Medium to start posting and put out consistent quality writing, but make sure they have a place to go to at the end to sign-up to hear more from you.