When I stumbled across a quilted portrait in my Pinterest search for quilts, I was mesmerized. I started searching for different styles and thought I'd like to try my hand at it. I bought a book called Portraits for Fabric Lovers by Marilyn Belford.
I got so much info from her that was helpful, however she uses more overhead transparencies and I am more software minded. So I took some of her ideas and came up with my own technique.
I use open source software. There are a few that I use consistently: Toolwiz Photos (Android). GIMP (GNU Image Manipulation Program) and Inkscape
There's a learning curve, but Youtube is invaluable. Several years ago I told an employer, "Yes, I can do that with Photoshop". I then went home and had my husband (who is a tech guru) teach me how. Once I learned the basics of Photoshop, learning other programs has been relatively easy. I'm told it's like learning a new language. Once you understand how to learn a new one, the next one isn't so difficult.
I'll go into the specifics of each program another time.