It's really hard to predict, throwing the grenade against moving targets has to be predicted and aimed where they're going. This is easier to do than the timed grenades and can be used to deny cover in engagements or push Riflemen away.
I'm not as solid with my OKW plays but you should try to have at least 2 racketens if you suspect a Centaur rush or use your volks to really force the Brits onto the defensive. In other words fight an aggressive game. It's always a good idea to get one or two arty guns against the brits because they really cannot counter it at all until they get a Centaur out and it has a good suppression value because #Reliccannotintobalance
Shreks can be used against centaurs IN SUPPORT of a Racketten-43. If you only have on or the other the Centaur will molest you like a catholic priest. But you have to win before a centaur comes out, deny fuel and you'll crush the brits. If you let them get to late game... GG.
its ok, i try my best, just now i beat a centaur with some stealing tactic style,,realy bleed but i did get the centaur
i got 3 Fussulier n 2 Volk 2 reken, fighting 4 IS, n Losing men, then i saw centaur
Reken aiming the Centaur 2 hit shot
1 Reken down, n So the other reken, but before the other reken Get killed i Immediate Stole the enemy AT gun that facing the Centaur
i win that battle with all my squad alive beside that 1 poor reken, i did manage to take 1 reken with me
n the enemy AT that i stole got kill by IS. Lose the game tho cause my teammate is losing almost all his unit to Air Supremacy