I know I'm probably late to the show, but here is an amazing website I recently discovered called Draw, Mix, Paint.
On this site, realist painter Mark Carder shares a crazy amount of valuable information covering his entire process. From toning his boards, to laying out a palette, to varnishing a painting... It's all here, and it's all completely FREE.
Mark has painted 2 Presidential Portraits, including that of George W. Bush.
I consider myself a pretty experienced painter, and I still learned a lot from browsing his video catalog. Mark seems to be the sort of artist who has advanced due to his strong technical ability and attention to detail. As such, he is very careful, well spoken, and quite good at explaining his process.
All of Mark's works are firmly grounded in classical realism. But don't let that deter you simply because you think it doesn't suite your style. Learning the fundamentals of classical realism is a great boon to any fantasy artist's arsenal.
I can not begin to imagine how much work it must be for Mark to create all of these videos. And to offer them all for free, simply in the spirit of sharing, is truly humbling.
If you like what you see, let Mark know in the comments section of his Youtube Channel. Or better yet, consider supporting Mark by purchasing his 'Painting Portraits' DVD. Originally priced at $129, he is now offering a HD downloadable version for just $20. That is a complete steal in my opinion, especially for 8 HOURS of material!
I am downloading mine now and am looking to forward to listening to it while I work tonight.