@matrixsasuke@fedi.absturztau.be
There are three ways (that i know) to do this in blender.
1.- With a solidify modifier and flipped normals https://yewtu.be/watch?v=5wu_SvCCX_U
It works in real time but it only works on eevee.
2.- With Freestyle: https://yewtu.be/watch?v=_QVNIEP1E5M
The downside of this one is that it's only visible after your render has completed, but it has a lot of tweaking options and modifiers available, and works on both render engines.
3.- With Grease pencil: https://yewtu.be/watch?v=a1o_W4XJvSY
I have not tested this one as i cannot use that blender version, but i have seen that while you have control too over the lines, it only works on a single point of view.
@matrixsasuke in the case of this image, the FACE object is using the first method, and the hair is using the second method.
Using freestyle allowed me to have a bolder contour around the hair and add some noise to the lines to make it look more hand drawn.
@matrixsasuke oh yes! and with an add-on you can export the freestyle line set as a SVG file, so you can edit it further with Inkscape or another vector software.
