Thank you! So, I usually browse a lot, and I also have a large collection of (mostly vintage) children’s books that I use for inspiration. Other times, it’s just learning to do things. So for example for my recent knight illustration, I thought to myself that I never played with reflected metal before, and I should try to illustrate it.
I use pencil on paper to sketch it, then I use a waterproof gray-colored ink pen to create the clean lines (usually 0.3mm Copic Multiliner or 0.5mm Uni Pin Fineline – sometimes a Winsor & Newton sepia-colored ink pen), rub out the pencil, and then I color it, usually using very muted colors or a limited palette of just 2-4 colors (otherwise they come out too garish).
After coloring it, I will use a white gel pen, white posca pen, Caran D’Ache Luminance white pencil, or white gouache to create extra highlights. Sometimes a Faber Castel white soft pastel pencil too. Anything to provide highlights, that make the painting look more dynamic. I find this is needed with watercolor, even if I leave empty regions unpainted to provide highlights. There are some very small highlights that you just can’t paint around (or use masking fluid that usually makes its edges ugly), so I add these highlights at the end.
For more texture, or to give some more emphasis somewhere, or to create patterns that are difficult to actually paint, I’d also add some muted colored pencils too. Never too colorful colored pencils, because they will jump out too much.