I gotcha back boi, I was doing this the other day actually. Just select a normal, round brush, then click at the top right hand of the screen, where there's a little tab labeled "Brushes." To make it look like a pencil, you need to play with the options in "shape dynamics." First, drag "size jitter" up to 100%, then drag "minimum diameter" to between 30% and 70% (just see how skraggly you want the pencil to look). "Angle jitter" should be at 100%, "roundness jitter" around 60%, and "minimum roundness" anywhere between 0 and 100 depending on how round or how sketchy you want the pencil to be. I also click the "Noise" option on the left collumn of options. And there you go. Should look a lot like a pencil line. I was trying to do the HOF poster when I realized I left off some of the info, so I just moused it in with the pencil-brush I made. You couldn't tell it was computer generated.