First sand everything down with 120 grid sandpaper.

For the larger gaps I would not use spot putty. Use a 2k putty instead. It is much harder and fills the lines better. You can also use a 2k epoxy putty like Miliput for this.

After filling, sand everything again with 120 grid. Then give it a 400 grid wet sanding.

Then apply 2-3 layers spray filler.... See more