You don't necessarily need a path if you draw things out by hand on a tablet or with a mouse but it might make it easier the first few times you do it. All you need is to set some scatter in your brush. Keep the scatter distance very low but up the count to 2 or 3. What this will do is slightly offset each time it puts down a dot and put down two or three dots. Another option is to use a mask. Make a mask of the lines then on the mask run the pixellate-crystallize filter and then smooth it out with the noise-median filter. I do this all the time for lumpy stuff.