Heavy traffic: Traverse the grindrail without hitting anything
Magician: Score of 4500 or better on the hoverboard race
You need the Grindboots: after you get the Map-o-Matic item from the Gadgetron Helpdesk Girl, Head out of the building and drop to the small platform below the grindrail you came off of and you will see a teleporter that takes you to the Gadgetron Employee Break Room. The gold bolt is in the break room.
You need the Grindboots: there are three activators scattered around the long grind rail. If you hit each of them with your wrench while grinding (and at one point you will have to take an alternate path), it will deactivate a force field that blocked the way to another grind rail. Once the force field is down, just flip to the rail (it's right before the second jump) and follow the path. Avoid or obliterate obstacles. The gold bolt will be on the grind rail.