I've found that a word flashing tool like this is helpful at first, especially for the people who feel like it isn't even possible:

https://tools-unite.com/tools/speed-reading-app

Using something like this, if I focus, I absolutely can read at a much faster rate than an internal monologue can keep up with.

Unfortunately I don't have any advice for a next step though. Looking at actual printed words on a page I can speed read, sometimes, but it's always remained too much of an exerted effort for me to take over full time.

And by the way research on this shows that comprehension doesn't suffer for people who are used to it.