for artistic billard, a silicon sponge (primary sold for shoes care) is used . not on the balls, but on the cushions, when the cloth isn't hot new.
it looks like this : https://fr.123rf.com/photo_5827652_eponge-de-chaussures-de-silicone-sur-un-fond-blanc.html
a few brands are good.
the applicaiton is "light", because if you put too much, too wet impregnation of the cushion cloth, then the result is crappy.
its primary goal is to make the table play much much longer, by decreasing the ball/cushion friction.
It is rarely applyed on the cloh itself, or on just the first 10-15cm of the cloth, from the cusion side.
such silicon coating is very efficient for some hours, and decrease shortly. BUT is it noticeable during days and days, if not weeks.
if this coat is good for aartistic, it is in fact not appreciated for the 3 cushion game (or worse, the balkline/small games) because it introduce too much artificial modification of the ball paths. In other terms, it can be used to make an old cloth to play a bit like a newer cloth, but it's not the same and the effects aren't stable in the time. even during a 50points game you can see the effects of the silicon to decrease ---> hard to adapt your shots.
Since in my poolclub we not only own 2 dedicated artistic billard 10' tables , but 2 pool tables too, I could recently notice than the effects of this sponge is less noticeable on a pool table than on carom tables . due to the cushion profiles I guess.
Note than in artistic billiard , silicon isn't used on the balls. never. Hot new balls, perfectly cleaned and polished, that's the best.
silicon used in artistic billiard : on cushions. but carefully....
about pool artists, dunno. may be Florian could answer, but IMHO with new balls & on a very fast cloth (like a simonis 300 fast) , i ain't sure than it is needed on the balls....