Painting grille area on stock bumper

I took the grille out of my 99gt today to make a grille delete (as I do with every stang i get), and the paint was chipped a little bit behind the grille, on the bumper. I barely touched it and a whole big paint chip appeared. It is only on the area where the grille goes, just the flat part. Could I just tape it off where its still good, and sand the paint off the part where its chipping, spray it flat black, and spray clear enamel on top? After I untape it will it be alright, as in the paint wont continue chipping off the rest of the bumper? That way it would just look like the black part that comes with the Mach 1 grille delete. Any advice? I want to get it fixed tomorrow. Thanks guys

but what i mean is, im going to have to tape it off, then sand down just the area on the bumper that needs painted, then after paint, the area that was taped off..is it going to chip and peel off

Hopefully working on it today. Any input appreciated