Being that I'm the one who has painted the most and largest S-I-L-V-E-Rs I'll step in here.
When you mix up S-I-L-V-E-R you will have something that is entirely different than Primer on your hands. The paint, one adequately thinned will literally pour out of the Gun....and that is a primary reason why Duster coats are absolutely the only method for application.
Determining how much paint needs to be applied overall starts with getting the paint's flow characteristics down pat at the start. There should be no surging or sputtering, but instead a "feeling" as the paint exists the nozzle of a constant noise and steady vibration.
The mix itself is so translucent, that even with the Silver Metallic in it, you cannot really see how much is laid down during the 1st-2nd coats. That is another reason why getting the speed and distance aspects of the paint's spray application is so important.
With everything being done correctly, once one has applied the 4th coat, and lets it dry, each subsequent coat will show up as a noticeable light sheen when you stand sideways to the Screen and look cross-ways over it. By the 5th-6th coats, the Screen should look to becoming very "silvery-white" in appearance. If it does, by the 7th-8th coat, upon close inspection you should see the entire surface have an even coating with no weak areas or areas where the consistency of the surface is different.
Increasing the number of Dusters is not what you want to do, especially if the Dusters are going up correctly. Nor do you want to rush into the next coat after you get the 4th coat up, because the application of such a fluid-like paint re-introduces a LOT of moisture. If there is much if any moisture still underlying the previous coat, you will create the tendency for a "slide/sag" to occur, or in the least start building up unwanted texture due to moist air in the previous coat getting trapped and trying to force it's way though the next layer, and that will create the little bumps that are in effect "Orange Peel".
All this might seem to make S-I-L-V-E-R seem to be a lot of trouble that is rife with potential failure...but it's not. It's really about the easiest of screens to paint. You just have to do the right thing repeatedly.
So if you have the Heebie Jeebies before you get started actually painting the S-I-L-V-E-R, PM me with a contact number and I'll call you to relate in person all the finer points needed to assure success.
If they are followed that is.... Post Note:
For a Screen your size, you should go through at least 1/2 Gallon.,...but not more if indeed not quite that much.