Painting Thin Lines

I tried to paint thin lines with an airbrush and some masking tape, however that did not work for really thin lines. It is possible to buy (rather expensive) special tools to draw these thin lines. This solution might save you some money. The scale in this picture is H0 (1:87).
These are some quick test examples. It is quite easy, but some practice is required. And start drawing and moving the ‘pencil’ before touching the object.
The pencils are needle tips in different sizes. They are cheap and can be cleaned with ease. I tried Vallejo Model Air paint and that worked well.

Note that the guide should not touch the object and needle tip. Otherwise the pain runs under the guide. This guide has one side that does not touch the surface at the edge.