I am building a car and would like to accentuate the seam of the car where panels meet with a dark line (sorry, I dont know the name of this technique - if there even is one) - I thought abouth using a sharpie pen, but i dont think the tip will be small enough.
Probably the best way to do that is with a wash. I use dime-store water color, with a drop of detergent in the water. The detergent makes the water flow nicely. Use the black color to make up a tinted water, then touch a brushful of this stuff to the seam. Capillary action will draw the wash into the seam. You can repeat as much as you need to get the depth of color you want, or wash it off and start over if you don’t like the effect.