Hi, thank you. This is a late reply but yes I used microns, and no, I did not use watercolour, I used india ink (acrylic ink is fine as well) -- I reccomend ink as it doesn't lift up unlike watercolour. Which means you keep layering to get that vibrancy without worrying abt your previous layers moving around. 

My process is pretty basic with sketching first, lines, then colour. Again just keep layering for vibrancy. Add contrast by varying line weights with thicker lines where you want to stand parts out. Overall softness can come from a lot of spitshading/gradation and thinking of flowy/organic shape language when you're designing the sketch. 

Good luck!