I'm not sure what you mean, if you're referring to the Slash vector, then yes, there is a certain, um, 'technique' for doing it. It's not that tough really, I could tell you how if you want to.

(Keep in mind I suck at explaining)
I use really thin strokes (thinnest in Illustrator is 0.25pt in line weight) and it also depends on how big your reference picture is. If it's really big, say, 1024x768, then maybe you could even use a line with only 1pt weight, but because you are going to fill in black in the end, so it doesn't really matter. I'm sure there are other ways of achieving (sp) this, but I don't know any other ways.. this is more or less how I do to get varying line thickness :
When you fill it black in colour;
And (just for the heck of it) -
For those of you who are wondering, no, I don't work for Rockstar Games.
Hope this helps, if you have any questions don't hesitate to drop me a PM, I'll try my best to answer.
