I know alot of mag writers, manufactures, and shooters advocate the smearing of some sort of lube over the ball after ball seating, but I gave up on that messy procedure 15-18 years ago. Instead, after alot of shooters do, I seat a treated felt wool wad that is impregnated with either a homemade lube or one that can be found for sale over the powder, then seat the ball. Precut wads of the appropriate size can be bought or punched out with a tool from felt, both of which can be bought from different sources.
I used to buy wads from Midsouth Shooters Supply in 100 and 250 quantity bags. I've read of some who say the lubed wad will contaminate the powder, but I've never had that problem, even when shooting in 90* weather. Sure, if ya load with a grease wad and leave the revolver loaded for a real extended period of time in hot weather that could be a possibility, but I don't know of anyone who does or needs to. I even treat wads with homemade lube differently depending on what type of weather I'll be shooting. The wads I used to get from Midsouth came prelubed, but I added a bit more which seemed to work better. Old felt hats can be used, also sheets of felt of varying thickness can be bought from Duro-Felt, a online outfit. Punches can be bought from leather craft or from various hardware outlets. There's alot of lube recipes I've seen on this site and others made from paraffin, sheep tallow, bees wax, olive oil, candles, etc.
The reason for is if you lube over the balls with some lube after ya fire the first shot you'll have grease all over the revolver from the cylinder/barrel junction forward. This is due to the flame exiting the cylinder/barrel gap melting grease on nearby grease covered chambers. The hotter the air temp, the worse it seems to be.. Yer hands will eventually be greasy also. Back in the day a grease rag was required addition when shooting greased over balls. Still carry one, but not for that mess. Shoot a cylinder full greasing over the balls and you'll see what I mean.
A lubed wad will lubricate the barrel from shot to shot and even help to scrub out the barrel when shooting. I can shoot alot of cylinders full of felt wadded balls and still maintain a clean foul free barrel. Check the Dark Arts and archives of the Darksider and you'll find alot of info on using wads vs smearing grease over the balls. Wads are less messy, IMO and from alot I've read of others who use them will clean the barrel better between shots, and seems to be faster loading a cylinder vs using grease.