I have had this problem many times using the matching paint such as 21st century paint but the fix is easy. and looks even better. After letting the part cure a day or two, I wet sand, breaking the surface with 600 then switching t 1000 grit (still wet) -a little dish detergent in the water helps. Once it is more or less even, rinse well then let it dry well ( I use my heat gun to dry it fast). Then spray a coat of clear over the part and voila.. perfect paint job. This way you dont have to remove as much of the base coat taking a chance of sanding too deeply and you will find that you don't have to get all of the orange peel off, just the majority of it. Wet sanding with fine grits takes a lot of time and you have to be very careful near any edges or raised areas as it will remove too much paint. Here is another trick. If you notice the orange peel while the color coat is still wet, shoot on a couple coats of clear first, then do the wet sanding. This sort of pre fills the low spots and makes sanding easier. For some reason the clear tends to go on less orange peel-ly then the color coats so it flows out and pref fills some of the low spots. I had a bad can of paint (21st century) that went on like sand! it was my last coat on a large plane and really messed up the cowl. I shot on the clear while it was still tacky, let it dry overnight and wet sanded the next day. One more coat of clear and it was perfect.. deep gloss, perfect finish.