This is an almost impossible question to answer. In 43 years of doing this no 2 cars required the same amount. Now take my 55 convertible
after the basic work was all done, each panel was blocked 7 times using urethane high build. Each final coat of the application of about 5 coats
was tinted with a different color so that when blocking was done the lows would be shown. Many years ago guys would come into my shop and see
cars with various different colors of primer and wonder if I was a mad man (I am 100% true) I would pull out a book on each car and I could tell
by what color the primer guide coat was based on that book, how many times each panel had been blocked. Some panels took less "blocking"
some more. The process will tell you what is needed.
Many of the paint companies will now tell you what shade of primer to use under their color coats to get the right color they have mixed. To light
will change the color, to dark will also do that.
Some times I like to tint my primer so if I know I will not need a lot of sanding=blocking. Then the top coat will cover faster with less paint. This mimics
a system that Sikkens Paint developed years ago. It was a system to reduce VOC's. They had a primer matching system where some of the colors
were used as the REAL color and then clear was used over them.
Tinted urethane primer over epoxy:
View attachment 397880
Minimal sanding and single stage paint:
View attachment 397881
Buy a gallon and all that is needed to spray it and get more as you need it. Let the project and work level you want tell you YOUR answer