I'm relatively new to Illustrator but am familiar with Photoshop. In Illustrator, I'm trying to draw semi-transparent strokes using the brush tool and it doesn't appear to be working. I've selected the brush tool, set the fill to nothing, set the stroke to a color, and slid the opacity to a percentage lower than 100. When I draw a line though, it appears with a stroke at 100%. I can select the line afterwards and lower the opacity, but this isn't very efficient. I've read several tutorials and I believe that I followed the instructions correctly. Am I missing something?