EG all the way! EG18's are the best for lots of smoke but are fairly big. The best ones i've found are the burst smoke as they smoke from both ends really quickly. (Problem is getting them)
I use Enola Gaye burst grenades with wire pull. Thge burst grenades produce a lot of smoke quickly but they don't last very long so its all about speed rather than waiting for it to produce cover. Every grenade has been perfect, I can't fault them.