Midas TouchG 20

Once you have all 75 Golden Manuals head over to the Bonus Room accessible via the portal. Then use the build station (at the center of the room) and build all 15 manuals.

If you want to make this super easy, you can enter the code 6LK78NN9 at the billboard located next to the police station in Bricksburg. That code will unlock construction pants which allows you to instantly build stuff at build stations.

Here's a quick video I made showing what this process looks like with construction pants: