55 chevy pickup cracked body filler

[wilberweb]

Hi, guys hope this is the right forum for this question.
I have my 55 Chevy 3100 Ive been working on. I was just able to get back to work on my project. My question is I have some cracks on the top of my cab where I patched the roof panel. It was caused by me trying to bend the inside roof side trim lip where the rubber trim goes on the roof of the cab.I had all of the top of the cab finished. filler installed where it was a perfect match to the other side. and I went and messed with the trim on the ceiling trying to bend it out a little with a pry-bar, and that's when I noticed some cracks. What is the best way to fix cracks in filler after its blocked and smooth with a perfect profile. I have some pictures of the cab part I'm talking about.

Thanks
-Larry