I just recently purchased a 2006 X15. It was in good shape being garage kept, but it had some light scratches and did not have a great shine to it. I researched a lot and finally did all the work this past weekend. The result was amazing. I know that the proof is in the pictures and I will post some soon. I did take pictures when I finished, but it was almost dark at the time and the pictures came out terrible in the low light. Just thought others may be interested in the materials and steps that I went through. Disclaimer: this worked for me, for others, mileage may vary.
1) I started off wet sanding the worst scratches with 1200 grit, then followed that with 2000 grit. (use top quality wet sandpaper from NAPA or another specialized auto paint supplier)
2) I wet sanded very light scratches with only the 2000 grit sandpaper
3) I then used 3M-06044 imperial compound with a 3M-05719 100% wool pad over the whole boat to buff out the sanding marks. This stuff worked great. Probably didn't need to do the whole boat with the imperial compound, but with an 8"' pad, it doesn't take very long.
4) I then used 3M-05928 Finesse-it with a 3M-05711 blended wool pad over the whole boat. played around with the Finesse-it and it actually would take 90% of the 2000 grit sand marks out by itself. The boat really popped after this step.
5) I followed this up with 3M-09030 Ultra performance paste wax, that I applied by hand (because it was paste). I used this on my old boat, but I am really not sure how I like it. I let it sit on the boat for about 1-1/2 hours and it was a b*tch to get off. The next time I think that I will try the 3M-09027 liquid wax and use a pad to apply the wax. I had bought a 3M-05713 blended polishing pad that could work for applying the wax. I have always used foam pads to apply wax to my cars, not sure how well the fluffy pad would work.
I bought a brand new Dewalt DWP849X to do the boat. This is my first Dewalt tool and this thing was rock solid. It is specially designed for polishing and it comes with the correct Velcro backup pad that works with the 3M pads that I list above. That saved me $50 since I didn't have to buy the 3M back up pad. I bought all my supplies from Amazon except for the sandpaper. Total time was about 5 hours, but a lot of that time was experimentation. Pretty nerve racking sanding the gelcoat for the first time on the most expensive item I ever bought, besides my house. So, I went pretty slow and cautiously at the beginning.
I also found this sheet on the 3M website that lists most all their marine products. The chart labeled "Buffing Pad Characteristics" was very helpful on selecting my pads.