How ro create a custom theme with dxpr and "drush" or "Composer"?

I have installed the theme and the truth is that it works very well. In any case, I have a question that I cannot resolve. In their instructions they indicate how you can create a "custom" theme, but unfortunately my hosting does not seem to allow the method they explain to create it, and I cannot work locally. Would there be a way to achieve this using "drush" or "Composer"? In the notes of the last update you indicate that you have improved the way to create a custom theme, but I can't find any more instructions than those shown on your main page. Can you help me?