How do I remove undercoating?

[CamarosRus]

I've been struggling to remove dealer installed undercoat from a 73 CAMARO project. This
is NOT a full original resto, but will be mostly original in general appearances.
After having this body on a cart elevated on jack stands, I used diesel to soften undercoat
and powerful pressure washer to remove most of undercoat.

I have now decided to mount body of rotissieri and have since flipped over
I am planning to use more diesel and more hot water pressure to remove remaining U.C.
I will then spray under floors with DAWN detergent solution and pressure wash
I will then spray mineral spirits and pressure wash

Will new epoxy Primer adhere to original Norwood Red Oxide Primer or do I need to
use paint stripper to go to bare metal ????
Will UPOL RAPTOR adhere to Red Oxide Primer if I decide to go that route ???

Thanks for your educated first hand experience/advice