For those who need a little lubrication we have available here in Australia a dry film lubricant containing teflon. It's a German product and is essentially a volatile solvent containing teflon powder. You spray it on what you want to lubricate, the solvent flashes off leaving the teflon behind. I'm sure that with a little imagination it's possible to devise ways to inject it into rudder cable guides to free them up. If anyone is interested I'll look up the product name and let you know what it is, I'm sure there will be other manufactures of this product and it should be readily available wherever you are.