Damn cable ties, that is a good idea! I've been messing with spanners, pencils, fingers, anything I can jam in the to be honest!
Just take em out, clean em and it'll be ok. They don't move very far in normal use and once the dirt gets caked up they resist moving back.
If you want to half try first you can eject the piston almost to the point of removal, clean the edges and push it back in. Works for me on some semi sticky ones if I'm feeling lazy.