On this page are links to PDF's that will hopefully get your head around stuff in Photoshop:

7 Mar 2021 - "Watercolour" - see here

7 Mar 2021 - "Black Ink Sketch - Postscript" - see here

28 Feb 2021 - "Black Ink Sketch" - see here

21 Feb 2021 - "Getting Extra from Your Textures" - see here

14 Feb 2021 - "Basic Compositing in Photoshop" - see here