Not sure why your #2 pencil isn't working better. Press hard. I use it most of the time on the vinyl/plastic blinds and it stays completely readable for a minimum of 4 years in full sun in my pots, way longer if protected from sun or underground. Since I cram a lot of information on my tags, I need a fine line utensil. Paint pens from Michael's last longer, but their fine point isn't very fine. The tip looks the same as in Lorn's pic. Not sure if it is oil based or water based. Not sure (and no one has said point blank) if one (oil or water) is better than the other.
Pencil does not work on metal blinds, even when they are coated.