.......sand the texture down with 180 on a DA sander.
if you have it up on its edge then yes it will create low spots. keeping it flat wont make low spots on the plastic due to the fact you're simple knocking down the texture, then spraying high build primer over it.
think of this, sanding by hand, unless you use a block will make it look like nothing but ocean waves. again, thats why the primer is there to block with 400.
And that's why you're the painter and I'm not. I have very little experience with painting. I'll make it run well, you'll make it look good! However, I do think that the inner dash panels will have to be sanded by hand rather than a DA, simply because of the amount of curveture. I don't think the DA will be able to access. The ones between the tank and the lowers should be fine to use the DA on. Of course, I was wrong before and I could be wrong again.
I know the Pusher stopped painting them awhile ago.
Is anyone else painting the inner dash panels?
What's involved in the smoothing out of the panels?
Is it something that I could prep and just get painted on my own?