I'm gonna be ripping out all the carpet and doing the whole cab floor in monstaliner as well as soundproofing the rest of the car. Shoul the monstaliner be applied to the prepped painted surface? Would it work better to apply it over a sound damping product? If so what? And for soundproofing the doors and wheel wells should I use a mat type product such as dynamat. Or a spray? What mat or spray would you recommend? And any other tips?  It's a two door softtop so I'm now it will never be "quite" but I would like it quiter. And I want to do the monstaliner right so it lasts

Remove the old asphalt sounddeadener, scuff the paint and apply the monsterliner. I would use a spray in sound deadener like Lizardskin. Monstaliner also acts as a sound deadener, quieter than the stock asphalt when applied to the entire floor of the tub.

So monstaliner without anything under it?

I had done several projects with both Monsterliner and Lizardskin, I found applying the lizardskin first under the monsterliner didnt increase noise reduction enough to warrant it. I would spray the sides and top and then apply the monsterliner to the tub up onto the Lizardskin. If you are going to have lizardskin exposed then I would give it a top coat of paint before applying the monsterliner.

If you want to really get into it you can go to the junkyard and scavenge around in the quarter panels of the cars there. Some use soft foam rubber sealed inside plastic (looks like a black garbage bag) stuffed between the inner and outer fenders to reduce noise. Grab some of those and stuff them in through your taillight openings if you haven't stripped the interior panels.