@ c2dfj45 shared how they do their sound deadener process, so this is exactly what I will do inside and under the car. Time to order some product.
@tornadoalleycruiser this is for you too....
Clean and prep metal.....on this truck we power washed, removed all OEM sound deadener, nylon brushed/sanded/wire brushed the whole floor(the floor was a mix of some paint that was adhered well, some not). Used the Master Series to seal up any rust(I think we painted most of the floor in this truck to 'seal' it). Scuffed the Master Series with 320 or what they recommend. We applied Second Skin Damplifier Pro FIRST(these are the butyl sound deadening sheets).....then we sprayed on the Spectrum....about 1-2mm I think. I waited a couple of weeks for it to dry just because we got busy with other things. 7-10 days is what they told me for the water to evaporate for full cure. We then knocked down the Spectrum with some 80 grit......then we sprayed our Raptor. The rear on this truck is raptor over the Master Series....no Spectrum back there. We did the floor in 2 sprays. I wasn't overly concerned with sound deadening on the rear floor....we will lay down some Luxury Liner Pro if it becomes an issue. Just the small amount of sound deadener we used in the Troopy is amazing....very nice inside. The amount we used on the 79 is ridiculous...that truck is next level quiet and solid.
On the 79s...since they are very clean inside and all new, we simply clean the metal, stick down the Damplifer, then Spectrum over it....no scuffing....and that was per Second Skin...however you can scuff if you want(red scotchbrite). When that Spectrum dries, it does not come off. We don't Raptor the 79s inside since they are all covered with flooring.
Since the undersides of the 79s are brand new and primed/e-coated, we do the same thing.....clean, then we roll on the Spectrum under the truck. You can use their additive to thicken it up(Sludge) and that allows it to really cling to everything. We do that in the cabs up in the corners of everything. The Spectrum can be used as undercoating.....it's solid stuff. I have yet to do a truck with it on the firewall(exterior...facing motor). I like being able to clean engine compartments. I think the Spectrum would be nearly impossible to clean.
I pull the tape on the Spectrum as soon as we are done with it and it's not wet to the touch. We re-tape when we Raptor.
The biggest thing on the 79 was doing the rear cab wall....again the same thing.....scuff, apply Damplifier Pro(we did the ENTIRE wall), Spectrum. Spectrum was used on just the exterior of the wall. I'm convinced that doing the exterior cab wall probably was the biggest sound reducer....that gap between the bed and the cab must have all kinds of sound and harmonics going on.
It's all really forgiving stuff....clean is most important. The only word of caution is that if you are going to spray the Raptor over the Spectrum, try to get that Spectrum as smooth as you can or you'll be loading up the Raptor to try and cover all the peaks and valleys created by the Spectrum. A lot of that is because of how fine we spray the Raptor....I think if you went with more of a heavier coat or texture, you're going to be fine. I love fine texture bed liner....hard to achieve that over Spectrum or Lizard Skin unless it's been sanded smooth. Hope that makes sense.
I'm wondering if the website saying you don't have to prime doesn't mean that nothing special is required. I'm sure it could go over bare metal but that sounds sketchy. Our primer is always Master Series.