Cool guy! Surprised you spent so little time on it!

Thanks! I make up time by using gradient maps for the colour stage, aswell as overpainting the sketch after the shading stage

Hm, sounds really interesting, especially about overpainting. Thanks for this information, I'll try sometime too! Usually I use black and white for volume and details, but it takes a looot of time to overpaint it

No worries, if you like to gray-scale before colouring, you can copy your grey scale layer, set it to multiply, paint a warm color, copy again, apply character color, then rinse and repeat using different layer modes i.e. color dodge! I tend to grey scale under my sketch, then overpainting the sketch in grey scale, essentially blending the sketch layer and shading layer together while adding minor details. If you can get your values right it makes it a lot easier to gradient map your colors later. Hope that makes sense!