Mine started making terrible sounds yesterday (sounds like big rain drops on the sunroof, pops over bumps). When I got home I put a generous application of silicone lube on all the rubber gaskets in the sunroof and it seems to be normal again...so it might need an application every few months or so to keep it quiet, unless it gets worse.
As for application to the entire gasket, you can do the front half by opening the sunroof all the way. To get the rest, I did the very back of the gasket with the sunroof tilted only, then the middle section by putting the glass backward a little to get the most clearance for my fingers. This was done by applying the silicone to a microfiber towel (that is now destroyed lol) and working it into the very slim space with my skinny fingers. Honestly, the real application solution would to get a tool with a cloth or foam applicator, like maybe a small paint brush with a foam head to get in there. Something like this would work I bet:
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