You could look at Anthony Waichulis. On his website, in his resources section, he has a bunch of useful stuff free for download.
He also has a forum - not free, but something like a dollar USD a month. Non-members still have access to quite a few of the sections, enough to get a good sense of the place and if it's worth joining.
You could check out some of his Vimeo videos. https://vimeo.com/user12850427
My favourites are :
A time-lapse excerpt from his instructional video.
Using a sort of stippling technique to even out thin layers of paint.
Same as above, but in the context of painting an object.
Using a stylus as a painting tool.
Painting a sphere.
Using masking tape to make sharp edges, problems, some stylus use.
Anthony's a trompe l'oeil painter, of course, not a photo-realist, but his work is made to withstand close-up scrutiny.