the key to garlic is peeling the few layers of skin off. My wife eats em by the handful (insert Al Bundy here LOL ) and likes them mushy, so they go in at same time as potatoes - just as i start the fire.
AS to the ice- i do that. and i find it does just the opposite...seals in the spices because the cold "closes" the pores and retards additional cooking.
Last two boils i forgot ice so i simply hosed pot off. I tasted the difference- not as spicy. But alas, im the only one in the house that likes em hot, so i get what i get and dont throw a fit lol.
and for giggles we did brussel sprouts - wasnt terribly bad either.