Chuck, one of the advantages of the ruling pen is that you don't ever have to deal with the end clogging shut. It will still sometimes get plastic glued to the two inner surfaces, but, when it does, you make sure it is empty of cement, and draw a folded sanding film through it from the "hilt" towards the "blade tips", and snap, just a couple of passes and it is clean. (kind of like a honing motion and speed)
Lol, you do have to hold it correctly, though,,,,,,,,when I was first taught to cement with one, I hadn't drawn with one beforehand, so I didn't know not to hold it by the "wrong sides", but, only by the solid sides,,,,,I had old fashioned Testors liquid cement going down my fingers toward my wrist. Capillary action works at all times, even when you aren't ready for it.
Rex