Polishing your car to get swirl marks out is like using wet n dry sandpaper. Start with a heavy cut compound and work your way back to a finishing polish. If you can remove a scratch with a cut comp. you'll need to work it back withy lighter polish to get the shine back.
You can get a good result and get lustre and shine with a quick polish but to get a premium result, multiply the effort X 5 at least.
Meguiar X is just a filler and the scratches will come back over time.
I'm a detailer and for an average job, I'll give the car 1 pass with a normal light polishing compound(1hr). Dark and red couloured cars require the extra effort to get a good result.
I recently did a black 2002 BMW M5 that had spent most of it's days going through touch carwashes. The paint was farked!!! 5hrs later and several hundred $$$ from the client had his car lookin' better than some brand spanka cars after the pre-delivery detail.....it only took 6 different grades of polish and 5 different pads and 16
passes and two passes with a wax. Some would say that much polishing would remove the clear coat altogether but that's not the case at all.
The biggest thing to remember with polish is let the polish do the work, avoid using too much pressure!!!!
Sing that song, puff all night long.......