>>7780581
This was something I did more for oil painting but applies fine to digital. Keep in mind that the proportions are observations that would be seen/made rather than what literally goes on the page. You should be able to visualize a box on the area of your drawing and the subject. These stages are done as explicitly as possible but you can have a lot more mess. You'll be able to deviate in some ways or prepare for steps earlier by looking ahead. This was mostly a blending tutorial but covers the general painting process and references some other materials. Really not much else will help than sticking to a method and doing more drawing.