Bumping will work if and when you back it up
with some kind of metal dolly's, when useing
a body type hammer.
Another thing I do on some crease's is to use
a #1 or #2 Oxy.Acet. tip, and on the under side
of the crease, draw a line in the crease to almost
dark cherry, and remove and let it cool. Most
often it will help shrink it back. Then use your
body dollys and hammer. light grind, sand, fill etc.,
prime and paint.
The big thing is to take your time, don't rush and
it will turn out nice. I hope this helps you.