No secret. Just whatever silicone spray they sell at the auto parts store. It's cheap and given how little you'll use, a can will last generations. You can even use it for its intended purpose of treating rubber door seals on your real car!
Just ordered my first ever set of brand new axles. Weird, considering how long I've been doing this. While shopping, I found myself drooling over the big bore dampers. I think the word "shiny" is involved. My ancient TRF dampers (early 2000s?) are still perfect and get rebuilt every year, but there's always the nagging thought that the new thing might be better. I hate that!