For Brenno, a pair of posts on materials and technique.
The pen I use 90% of the time is from a Japanese company called Muji. I found the pens in France, and now I order them through the mail from England because I can't read their French website. Here's the Muji site. Their wonderful brush pens are HERE. Just £ 2.50 per pen from the U.K. But made in Japan.
Here's the pen (on the bottom) compared to a typical felt-tip brush pen, in this case, the Faber-Castell PITT.
Here's a tip comparison. You'll see right away why the Muji allows such thin lines.
The Muji is cheap (about $4.00 U.S., plus shipping from the U.K.), and even when the tip goes, you can use those brushes for dry-brush and halftone work. And although they are not reusable (no refillable/replaceable ink cartridge), the ink lasts a while--much longer than the tip!
Here's that new Muji compared to one whose tip has been frizzed by inexpert use (read--me drawing with it):
Rough, then grid - Super rough, then I made a grid to match parts, then I moved other parts to better match the grid. Then I'll light table. Got three to do. Moon colony ...