When I used to do this work, I would use a dolly, body hammer and also cold chisel to make the square edges required - the gaps are set by shaping the edges of the fender skin to the bonnet, once it lays perfect - use a vernier to check gap all the way, then get the shape correct for the grille, I found it easiest to make a cardboard shape of it then work the metal.
it would take me about 2 hours a piece including hammering, body filing and levelling the fenders.
Its a learned art - quite hard to explain in words.
If you want to reshape it now - you will have to refinish the fender paint.