There seems to be a gasket set available for these - trx7781 or there are other ways to diy a gasket if so inclined (paper bodge, gasket paper, instant gasket etc.) to stop the leaking.
As for grease I’ve used boring lithium grease for all things rc for many years. I will however be trying some “red n tacky” in the future. It’s an extra sticky lithium grease basically.
That moly grease stuff would/should also be fine but iirc lithium is better in/around bearings.