Sorry, now I understand!
Here's what I did just to clarify!
Basically what i did was use spray on 2k 'synthetic tar' sound deadener underneath the car over the top of a couple layers of primer paint, then had final coats over the top of that... (so it's all white...). Then painted the wheel arches black over the top of that! I had the interior painted straight over the sound deadener matts (as you can see in the photos).
This I thought would give the best resistance to debris undneath the car, and at the same time stop the panels from resonating when driving or debris hitting them. In addition to this, just painting the interior of my car without the deadener sprayed on, I thought was easier because I didn't have any rust, and I didn't want to add too much to the over all weight of the car. (only a couple of Kg, but it all adds up!!) Plus I would've been doubling up spraying it twice.
One of the reasons I ended up painting the underneath of the car first and then put the deadener over the top of that is it provides a chemical bond for the stuff to stick to, and also if a stone breaks through (or anything else for that matter) you still have a layer of paint helping you out in the surrounding area! My advice if you are going to use the sound deadener is to by a 2K version, and spray it over already painted areas. (primer is OK) then put your final coats of paint over that.
Also because I want to fit a cage, not that much effort has been spent on making the interior metal look 'clean' because the car to me is going to be a street legal race car, not a show car. If it was going to be a show car I would've used body filler to even out all the seems etc. etc. To me personally it's not worth it.
What are you doing with your car? I know you have been discussing this heaps!