This seems daunting, but it is actually quite easy, and will take about 15 minutes on a bonus play.
After you beat the game you will have costumes unlocked, including the one that will help you with this trophy immensely: the "Spud of War" (makes Kratos looks like a giant baked potato
This costumes grants infinite magic. And with a bonus play, you have everything unlocked. You just need to play to the first Basilisk encounter and, once the mini game is promoted ("O" above the giant lizard's head) keep hitting the beast with the Light of Dawn attack. Your magic won't run out, and the boss will continually get his life back, but with a maxed out spell on the lower difficulties a couple of hits will reactivate the mini-game.
Spamming the crap out of that spell got me the trophy in about 15 mins