The teammate doesnt have to do anything... its YOUR weapon. When you target an ally with poseidons hammer square it turns the wave into a jumping spinny kratos thing. When you hit an ally with athenas blade square it puts a shield on them. Its just variations of your own attack not like coop button prompts for your teammate
lv 9 blade of poseidon / centaur spear both have co op moves posidons l1 square turns into chain based attack and minotaur spears l1 triangle uses ure teamate as a stepping stone by running up and jumping off them into the air and plunging the enemy with ure spear with a sheild around u .