I'm in the middle of the same project myself.
What I've done so far:
1. Chipped off old sound deadening pads from floor. Ripped out carpet.
2. Paint stripper removed the adhesive residue from carpet and sound deadening well, without removing the factory seam sealer or primer.
3. Goo gone spray gel removed the remnants of the side pads (seen in first photo of post #9 above). Let it soak overnight and it came off pretty easily.
4. Mineral spirits to tidy up after the two chemicals above.
5. Scuffed the surface with some sanding sponges. Vacuumed dust.
6. Cleaned the surface with 3m wax and grease remover (Xylene)
7. Primed surface with 2k epoxy primer. Bought two cans for both floors and the firewall, and came out a bit short. Finished it up with some primer from home depot.
(
these guys have great prices on paint and supplies. I couldn't find the 2k primer locally.)
8. Next up is spraying down some
Lizard Skin sound deadening on everything that resonates - floors, wheel wells, firewall. Then topcoating with something nicer looking... thinking satin black or grey.