How to highlight panel lines

I would like to know if there’s someone out there who could tell me a good tip for highlighting panel lines. I’ve tried to use acrylic mixed with water and a small drop of washing up liquid and I used the same technique with Chinese ink (on my test model), but I ended up with some ugly stained paint with spots that I cannot wash after it dried. If I wash it when it’s still wet no paint will remain on the panel lines. What am I doing wrong ? [:(]

use a micron pen, or use PAINT AND WATER

I use a Rotring Rapidoliner – .18mm – for black lines, and an extra-fine drafting pen with Flannel Gray ink – Private Researve – for most things. I thing the dark gray looks a bit more realistic that a true black.

If the paint wound up stained, I wonder if you had a clear coat on top? Just about every technique I’ve heard of requires a glossy clear coat first - that allows you to wipe away excess without it staining the paint.