This is also such an amazingly fun way to practice highlight placement as well.

And Happy Valentines day to you

Cool sort of fantasy palate cleanser.  Nice, refreshing results!

The tips on the 2 color thing for highlighting and trusting the process should help me with my brickwork.  I was struggling with getting free handed ones on a flat surface to look right.  The less is more and moderation with the black lining is pretty important and I'm glad you emphasized it.  I made the mistake of using it on chain mail, and at working distance it looks fine, but once you pull away to a normal viewing distance it just muddies that whole section.  In general with the black marker I found running it on an edge like corners works pretty well, like an inverse edge highlight that is way easier to do with a mostly solid application method.  It works and looks especially well on edged weapons that are a bright enough color.

Excellent stuff,stay well mate

Satin finish works well as an all rounder and will give a touch more color depth due to extra highlights from the sheen, but a matte finish can further sell the 2d look by 'flattening' the natural light to be more uniform.  There are probably some ways to mix and match those to greater effect but I haven't dabbled into it too much.

Interesting technique, like this style! A friendly suggestion - try thinning your paints a litthe bit - they will look smoother and easier to spread.

Which black paint marker did you use? Was it acrylic, if so it stuck to hobby paints okay?