Seems the Rain-X (I remembered the name finally) would be ideal both dry lubrication and water repellent and as you can see, it dries and is clear since its on glass. Oh well, just a thought.
CAUTION!!!Unless you have actually tried any specific material on solid lines, please do not even suggest for others to try it. Rain-X and some other materials like it
DO NOT WORK unless you want to have sluggish or locked up controls which will usually happen. Yes, one application of some of these materials might act like they help, particularly when it is raining. The problem will come up with the thinking that one application worked OK, the second application should be better.
WRONG!!! If you use any of this stuff, even talc or graphite (or a mixture thereof as some use), the lines need to be scrupulously and often cleaned before extended use or any further applications.
Besides, solid lines should be thoroughly cleaned after several flights, particularly in areas where smog is prevalent (like any field in LA).
Keith