I repainted my rear fenders. The fronts will be done next winter. Here is what worked for me.
1.) After sanding with 120 I sprayed on a coat of epoxy primer to isolate any paint left and to protect any bare metal.
2.) Two coats of Black Feather Fill primer surfacer.
3.) Block sanded the entire fender top and bottom with 220.
4.) Three coats of Urethane Black Enamel.
5.) Color (wet) sand top and bottom with 2000 through 5000.
6.) Buff out both sides.
They came out very good. But it is a long job. It was my winter project, and I used the entire winter! Much of it is dirty dusty work - not fun! If you have the time and the desire, go for it. The worst that can happen is that you can screw up and have to sand it off and do it again. (Don't ask how I know that!)
You will learn a lot, and gain great satisfaction when it comes out great. However remember that if it does not come out good there is no one else to blame other than yourself.