Thomas Blackshear has produced a series of instructional videos called the Illustration Master Course. I have had an opportunity to watch most of the videos in the series and can highly recommend them.
If you're not familiar with his work, Thomas Blackshear emerged in the '80s and '90s as an illustrator, creating about 30 US postage stamp designs, plus posters, art prints, and 3D figurines.
He trained in Chicago and worked for Hallmark Cards and the Godbold/Richter Studio.
At that stage of his career he was inspired by Mark English, Bernie Fuchs, Drew Struzan, and David Grove, and he either learned directly from them or figured out their techniques.
The first volumes in the series demonstrate these unusual techniques with gouache and acrylic.
In Volume 4 he demonstrates the "lifting out" technique, where you apply a gouache base layer over a pencil drawing and lift out light areas with a wet brush or Q-tip.
He has since pursued a gallery career for his original paintings, developing his own style that he calls 'Western Nouveau,' inspired by a variety of painters of the past such as Maynard Dixon and Alphonse Mucha.
Most of his gallery paintings start in acrylic and finish in oil, sometimes with special touches of gold leaf.
His videos take you through the entire process, with closeups of his palette, his brushwork, and his special techniques, which he explains at each stage in a clearly recorded voiceover.
The video occasionally cuts away to him sitting in his studio explaining the thinking behind what he's doing. His process is 100% 'old school,' using pencil, brush, tracing paper, and acetate overlays.
He often does a very detailed and complete pencil drawing and several color studies before he starts the finished painting, and the quality of his final results proves the value of solving all the problems sequentially.
Blackshear puts a lot of emphasis on getting the drawing right, no matter how much effort it takes, before proceeding into the paint. He hires models and shoots photo reference, but he freely interprets his reference to make it better.
There are six episodes so far, produced by Thaxton Studios. Each video is about an hour long, and priced at $45 for either a download or a DVD. Each is a standalone exercise and you don't have to follow them in order. I would suggest starting with whichever one that sounds closest to your interest.
You can get info about Thomas Blackshear's Illustration Master Course at this link. The videos are also available at Gumroad as digital downloads or streaming videos.
Muddy Colors did a blog post featuring his gouache 'pick-out' technique as featured in the magazine Step by Step Graphics. (Thanks, Matt Dicke and Dan Dos Santos)