even though spraying the panels seems like the easier thing to do (no measuring, no cutting and applying film) it is a misconception.
for one thing as mentioned before, it is somewhat technique sensitive and the spray does not act consistently even from one can to the next not to mention when the spray finally cures which could take a very long time if the conditions are not ideal the surface of the part is not as smooth as compared to film. It is still a good product and has its uses but the two small panels I did took over three days to cure by comparison I did the large thin middle panel in just a few hours and it was done. other thing to worry about with the spray is that the material has a tendency to run and if you overspray you would get an inconsistent thickness and run lines but the film is more uniform when applied... as for the level of protection I cant be certain but it seems that the film would be stronger however you could over spray a part and make it very thick so anyones guess there
as far as how many hours I really cant remember I took such a long time because I was not in a rush, we took the panels out in one day and I slowly began working a little at a time and experimenting with the spray and film to get the results you see here. If i had to guess I would say on average 3 hours per panel.