On offense its not all tha useful because smoke is directional and is fired on position where you tank is right now, so if you move more forward it will be useless.
Heh, yes. I don't think the tank smokes are not to be used in offensive (excluding the churchill fart).
But the mortar smoke barrages, or offmap Ju-87 smoke drop. They could be used to screen infantry rush through enemy MGs field of fire, or to cover pioneers while setting mines or defusing enemy mines, yeah?
Judging from your answer, Hector, i assume you haven't ever thought of using any other smoke than tanks smoke? Just joking, but really the question is: is the smoke ever used anywhere and is it succesful or not?