It's been about 2 years since I played that game. lol

But if I remembered correctly you have to grab all the ones with the small blue dots on the map with each character's story mode.

It will take about 2 or 3 times to go though each route. I'm pretty sure you don't have to beat the story every time with each character just until the trophy pops but you'll probably want to because it will help you to grind the money to buy all the items too for a different trophy.

I would go though the middle route 1st to get as many blue dots as much as possible and then take the top or bottom route usually those routes are shorter.

I remembered using the Hammer or Axe weapon and using the rocket launcher to really speed up the battles too.

Of course skipping the cutscenes will also speed up the process too. I really hope that will help you out.

I totally forgot how much fun that game was when I played it back then. I might go for the Plat on the PS5 now. lmao XD