Paint dull after wet sand

[baddogbo]

Thanks for looking, I just completed a auto boby course to do some work on my 72 mach 1 after getting body shop prices to repair minor rust in the door. I wound up compleatly stripped the door welded patch panels filled and painted on my last class. It actually came out better than I could have hoped for but even in a paint booth it wound with some dust or whatever in the paint. Teacher told me to wet sand with 1500/2000. I did but now paint looks dull. Class is over teach not around what do I do? Any help appreciated.
Thanks
Jon