Super Coverite - is actually a fabric and does very well in simulating fabric covered aircraft. Iron on using lots of heat. Needs to be painted after application. Is the "only" stuff to use when building a scale fabric covered airplane.
Super Shrink - is more like silkspan in texture, lighter than Super Coverite. Applies very much like monokote, although more heat is needed. Needs to be painted after application.
Perma Gloss - is Super Coverite with a pre impregnated color. I am not sure what the coloring material is, but it appears to be some sort of latex paint. Applies like Super Coverite, but does not need to be painted and is fuel proof.
As with all things model airplane, if you can half of what you paid for it, you're doing good. As I recollect, the rolls were available in varying lengths up to 25 feet. Originally, the stuff was somewhat more expensive than Monokote.
I understand from another modeler, that Perma Gloss does not shrink up as well as the other two. Super Coverite is still available through Tower Hobbies. I don't think they make Super Coverite any longer.