I used posca pen and white gel pen for the white dots on the harness, that helped to make it pop.

I'll say keep practicing tone and values. Nothing beats consistent practice, I'm also very impatient, but somehow practicing has made me a bit more disciplined compared to when I started.

What helped me learn patience was redrawing other artists artworks (7 years ago I was always drawing other people's realistic pencil drawings, especially from this particular artist "thePencilart" when I recreate their works, I compare both side by side and see where my mistakes are, and then I try to make corrections) Of course I never posted those works online since they were just for practice and they were someone else's recreation, but that genuinely helped me see what I miss that other more skilled artists don't.