I would reccomend using DP90 before filling.
It adheres better to bare steel than body filler, and filler adheres better to it than bare metal.
As far as self etching primers DP90 is probably one of the best.
These AD fenders have a double crown,and it's more important to get them smmoth than straight,any waves you might have will not be visible, even if you can feel them with your hand.
If you only have a minimum of filling required, you might want to try a 2 part glazing putty,it's just like body filler with a
finer consistancy,and sands MUCH easier!
When you have your filler finished,reprime with DP90 followed by surfacer.
If you over work the metal,you could end up with stretching,which is a whole nother topic!
From the looks of the pics,looks like you're about ready to proceed to the next step.
Good luck
