Mostly I write on forums like this one, and have published one book, How to be a School Bus Driver as an Amazon Kindle book.
The last 20 years of working were driving a school bus as one of the many pieces of income. More on that here:
https://davebross.com/resume.html
It was an awesome part time job, at least for someone of my temperament.
As far as actually writing,
I do best with writing for a few lines or a paragraph then going back to edit, then editing the whole at the end.
Something as long as a book I'll make an outline first.
The edits are usually stripping out any unnecessary or unclear wording...which there are a lot of for me.
Stuff like every "and" or "but" are usually places you should have ended one sentence and began another.
Naming specifics instead of using a pronoun.
Minimal if any adjectives.
I had to write a lot of the course material when I taught in Job Corps and they wanted no more than five words per sentence and five letters per word. That's a very effective format considering how badly the education system has damaged reading skills for so many. I think current US average reading level is 4th grade equivalent. It also makes for quicker, easier writing for you.
As far as what's going on in self publishing currently ...an ever moving target...here's a good resource:
https://kk.org/wp-content/uploads/2025/08/Everything-I-Know-About-Self-Publishing.pdf