Rudder lines cleaning and lube

So it's getting harder to pull on my rudder lines and it isn't so smooth anymore.

How do you guys keep 'em clean and what kind of lube do you guys use that's safe on PVC?

Rope wax

Some recent discussion here:

http://www.norcalkayakanglers.com/index.php?topic=84863.msg964724#msg964724

And some discussion on the Hobie forum that might be useful too:

https://www.hobie.com/forums/viewtopic.php?f=11&t=60307

Thanks for the tips and related threads guys. I ended up going with a can of silicon spray. Should do the job.