Sean, interesting stuff. I just went to their web site and read about lizard skin. Here is a quick guide they use for how much you will need.
Older style Pickup
1940-1960 2 gal. - 1 unit

3-5 Window Cpe 2 gal. - 1 unit
2-door Sedans

1933-1939 4 gal. - 2 units
Chevy/Ford

1955-1957 4 gal. - 2 units

Applying LizardSkin® Ceramic Insulation & LizardSkin® SC
For maximum sound control and insulation performance, both LizardSkin coatings may be used, but it is important that LizardSkin® SC always be applied FIRST. When used in tandem, LizardSkin® SC should be applied at least 12 hours prior to application of LizardSkin® Ceramic Insulation.