I'm looking for an add-on or a short cut to fill fast and symmetrically a complex surface that needs to be closed with vertices. Doing it manually it takes a lot of time. I tried to do Ctrl+F and then Grid fill, but it didn't work. Neither F key works. Check the attached screenshots.
This is the surface that needs to be completed with vertices :
This is what happens when I try to use the Grid fill tool :
And this is what happens if I try to use the F key :