I have taught the art and science of astro-image processing since 2005, via video tutorials, books, and one-on-one private lessons.
Feel free to contact me privately, or to sample our instructional materials at the following links. 
 
Email me
Ask questions or book a one-on-one session
Masters of PixInsight 
A PixInsight-centric teaching resource, also covering Adobe Photoshop and other software 
Inside PixInsight
My book at Springer Nature, also available at Amazon