Here's a link to a guide I made. It has a full story walkthrough and the details for all collectible locations.
http://www.gamefaqs.com/xbox360/722935-the-lego-movie-videog...Use Ctrl + F "Red Brick: Studs" to find the locations of all the multipliers (x2, x4, x6, x8, x10). You can get the first 3 as you play through the story but you'll need to wait until near the end/after the story for the other 2. Once you have all 5, activating them all will give a x3840 multiplier. Having them all active as you go through Free Play levels for collectibles will make this achievement come in no time.