I don't know if XMT#4 is hyped, but the lack of result is probably mostly due to the limitations of the PC. That being said, you could try again using a couple of slow passes with XMT#4 on a cutting pad, followed by XMT#3 (or 2) on a light cutting pad, and then XMT#1 on a polishing pad.
BTW, if the scratches are so deep that you can feel them with a fingernail, you shouldn't remove them no matter what tool you are using, as you would be removing to much clear in the process. This could leave to early clear coat failure.