My car is a gunmetal grey JDM. The front bumper in 2 places has faded with the sun and is slightly rough to the touch. Whats the best thing for this? T-Cut? Something stronger?

Obviously my plan is to bring it back to stock shine!

Well it sounds like a job for a respray if the paintwork is rough to the touch, but before you do that you could try the following:

 

Use some rubbing compund and a machine buffer.

Check the surface is now smooth and apply some T-cut to the affected area.