Priming In Small Sections – Question

Below is the questions emailed to me.

Hi Donnie – I love your website – Have learned much from your videos and blogs…. But I need a little direction… I have attached 2 photos of my 65 Chevy C10 that needs a lot of love. I am a DIY-Guy and can only dedicate a few hours a week to work on her and sadly she is not garaged and is exposed to the Florida sun and rain all of the time… I need to do small areas of rust & body repair at a time sanding off the surface rust, filling and priming… I have a Devilbis Starting Line Paint Gun Kit.. So here are my questions…?
1.  Whats the best approach…? Should I sand off the rust to bare metal and prime without using filler or glaze for now just to get her protected and then go back and sand, fill, glaze and prime again before final painting..?

2. Because I will be prepping small spots at a time (1 to 2 square feet) what is the best primer to use..? Knowing it will be exposed to the weather for long periods of time before final prep and paint and knowing that I will have to go back and sand the re-prime the entire truck before final painting…?

3.How long can you leave the truck in primer….? It will take me a long, long time to get to final painting and the truck will be out in the Florida sun / rain..? Should I Paint a her with a temporary final paint – go back and repaint all later…?

4. If I use an epoxy primer – I will be setting up my spray gun and cleaning it more than actually painting.. suggestions? Use the smaller detail gun…?

Thanks in advance for your help…