The liquid in my USC contains some ammonia but has some slip to it, and is what my jeweller friend orders in bulk. I've regularly used it with many brands of plastic pens without any problem. You have to rinse it off with plain water afterwards.

You would have to be able to shake the water out to get the pen dry. I don't know what your barrel/piston currently looks like so don't know how well that would work.

Anyway, good luck with whatever you decide to do with your pen.