I've done something similar, originally using dielectric grease (which I still use on rubber trim), then switching to silicone brake lube, then after a long term trial (per each individual tube age, not per brand/model), I'm now using a very old tube of GE Silicone caulking that never sets... after long enough, the acid in it is gone, no longer smells like vinegar so then (not before) it is ready to use, and eventually it gets less wet than the dielectric or brake grease so less dust and grime sticks to it, but it never gets to a point where it's rubbery or lifts off as a white film like cured caulking can.
It's not a long term solution but neither is paint, yet in many cases paint looks better... but paint is more work and expense, when it's not like we're talking about restoring something to new condition.