It's been quite some time since the time I said I'll share my technique (to some people). So this post is on this topic. I'll share my secrets to you, okay?
Any suitable surface to doodle
Permanent Marker (I personally love Faber Castell Multimark permanent marker)
Acrylic paint or fabric dye (for base coloring - give you a smooth surface to doodle)
Clear spray (just in case water spilled on your artwork!)
Ps - You don't have to create outlines using pencil first then do the inking. You can just doodle using the permanent pen. No worries. Practices make perfectto~*