Auto body repair & detailing: Black Paint Blending Problem, rear quarter panel, ford contour

Question
I just completed a rear quarter panel/dog leg rust repair on a 1997 black Ford Contour.  I used spray cans of basecoat and clearcoat from a local supplier, which sprayed very nicely.  The body work and paint look great, except that there is a very noticeable blend line from new paint to original paint.  The new paint and clear are on the quarter panel only; they were not sprayed on adjacent panels, so the blend line is on just one panel.  I sanded the new and old clear with 2000, then polished and buffed and it looks great, except the blend line is awful!  I realize the original paint is 12 years old and is faded, but I think I did something wrong.  The paint is straight black, no pearl, no metallic.  Thank you for your help.  

Answer
JOHN.....YOU ARE NOT GOING TO BE ABLE TO BLEND EASILY WITH SPRAY CANS....THE PRESSURE INSIDE THE CANS FLUCTUATE TO MUCH AND WILL MESS EVERYTHING UP. WHEN BLENDING YOU HAVE TO GRADUALLY MOVE THE
BASE COAT OUT INTO THE BLEND AREA AND THEN CLEAR THE ENTIRE PANEL.

I THINK THAT YOU MAY HAVE TRIED TO BLEND YOUR CLEAR AND THAT IS WHY YOU SEE A BLEND LINE.
RE SAND TO REMOVE THE BLEND LINE AND RE CLEAR THE ENTIRE PANEL....THAT SHOULD DO WHAT YOU WANT.

GOOD LUCK