DP/DPLF has Higher Bite properties to Raw metal then body filler, therefore PPG reccomends it down first then your body filler, this why you dont have such deep scratches to fill on your repair , and it useless to use DP/DPLF as a sand scratch filler , THATS NOT what its designed for !!

I am not saying your way wont work as its been done that way for years with no ill effects. But PPG
still wants protection between your bare metal and body filler.

We are on a HOTROD building forum where doing it right with no time frame on getting it out the door quick is not the subject.

I dont do the way i posted at my shop as it is VERY time consuming, I let my body men grind and fill over bare metal too , as time is of essence, and I use NCP 271 over the repair as it has metal etching properties built into this product. But I dont let them send the repair to me in anything courser then 150 grit, as this is where time in the paint shop is , as it requires too many coats of primer or a block and reprime . Time wasted and product waste.

Spray