>>96336968
Just use a micropen. I have a bunch of sakura micropens in different colors. If they are document proof they are waterproof, i.e. you can paint and varnish over them with a brush as well. Just give them some time to dry. I found that after ~45mins there is very little smuding and after 4h you can stab them with a stiff brush and nothing happens anymore.
Great for blacklining, freehand detail or eyes.