The professional way to blend a paint repair is to spray a clear base over the repaired area as well as the ares adjacent to it then spray a progressive thin pain coat on top until even. Go full color on the first coat but the additional coats by half with clear on every additional coat.
I recommend you get a hold of a air brush. The ones used for model cars etc.. You are going to lightly paint the damaged area blending as you reach the outer edges. Keep doing so until you match the origanal paint of your car. You should try to purcase the same brand auto paint.
I hate to tell you this but you dropped blend new and faded paint. Once the paint is faded, the only thing you can do is repaint the whole car or have one spot look different from the old parts of the car. I am sorry to be the bearer of bad news.
Sand, prime, paint, sand, prime paint and repeat, the key is to vary the pressure on the edge, sand it lightly it would be perfect but the point is to avoid a dramatic change.