Weighing my options...

[SmashingPunkFan]

Self etching primer always goes on thin like water, I always cover it with a coat of epoxy & 2 coats if it's going to be sitting around a while & don't do what some people do, Some people think OH, Now that I got the bare metal primed with 1 coat of etch or epoxy, I can now let it sit outside in rain & winter for next 10 years. LEON.

Ahh, I see.
And what's a good quality, but cheap brand to use? Cause it'll eventually come back off

SPI epoxy. It is cheap, high quality and free shipping. Just make sure to follow the rules to the letter and you'll have great results. Don't even bother with etch primer.

If you want to do it right then you cover all clean and bare metal with epoxy. It is the only primer that is waterproof. Then do your repairs on top of that and always re-epoxy bare metal before going to the next step. You can spot spray it, you don't have to redo entire panels when you sand through to the metal. When you're ready for a high build primer shoot two more coats of epoxy, let it dry for 1-7 days and follow it with a few coats f high build primer. Sand and repat until you're ready for paint, then shoot thinned epoxy as a sealer followed by topcoat. All primer and topcoat let water through like a sponge so having all the metal sealed by epoxy is the way to go.

Thanks for all the info.
I've gotten nothing but mixed messages about primers, and how to use them.
The environment I'm working in is subject to moisture in the air, not directly dripping on the car. And very dusty, but it's all I have. And I've been covering all repairs with self etch unfortunately do to previous advice.
So sectional working is definitely what my options are.
Are these epoxys available in spray cans? Or do they come in pints only?

[Dino]

They come in quarts, I don't think they sell pints. But it's less than $40 for a quart. There's no real epoxy in a can, you need to mix it with activator. There's a brand of spray can paint with an activator you mix just before spraying but don't bother with those. Etch is what we used before we had epoxy. It still has its uses but not here. Epoxy is the only primer you should use on bare metal, period.  Prep your metal right and obey the SPI rules and you can stop worrying about moisture. 
Be sure to spray the inside of the panels as well though or this is all a moot point.   

[SmashingPunkFan]

Be sure to spray the inside of the panels as well though or this is all a moot point.   

That right there is gold info. All of my rust bleeding issues have been from the inside panels leaking through a welded void or pin hole. I'm trying my damnedest to make sure everything is sealed tight, but it's very time consuming and challenging.
Slowly it's coming along though

[SmashingPunkFan]

For anyone who has used POR15, what is the worse condition metal you've applied it to?

I have some sections that are very rusty, and would require several more panels and about 2k in money.
But if the metal is still internally strong enough to withstand its duties as under roof skeleton,  then I will use alot of por15

[new2muscle]

 Two things...

I fully agree that SPI expoxy is great stuff, and they are great people to deal with.

http://www.southernpolyurethanes.com/

I have had good luck with using POR15 on metal that hasnt been penetrated all the way through, I used it to paint the entire underside of my 70 charger. Problem is the price. I found a substitute (Chassis Saver) that IMHO,  works just as well for me, same benefits and drawbacks, just a bit cheaper.

http://www.magnetpaints.com/underbody.asp

Only problem with POR15 type products is that is isnt easily sanded, so use it where it wont show or where you know you wont have to do any finish work. Spraying it isnt hard, but it levels REALLY well and you can just use a brush and get great results. Under-side-of-the-car type places and floorpans, etc. I applied mine by brush, and you cant tell that it wasn't sprayed. Pretty damm messy tho......painting upside down.

POR15 makes a putty as well.... I used it on the roof for some corroded spots. Its just really thick POR15.

Have fun !

[new2muscle]

One thing I forgot.... just make sure you mechanically clean all the surfaces first. Aggressive wire wheel all corroded areas first, degrease, then apply POR 15.

[SmashingPunkFan]

One thing I forgot.... just make sure you mechanically clean all the surfaces first. Aggressive wire wheel all corroded areas first, degrease, then apply POR 15.

Awesome info. Will do on the prep stage.
The under body is a great idea, I want something to keep it all safe

[new2muscle]

  Take your time and have fun....

  If I remember, it took 2 quarts to do the whole underside of the car.

[SmashingPunkFan]

  Take your time and have fun....

  If I remember, it took 2 quarts to do the whole underside of the car.

Always having fun with this if I'm not enjoying it, I stop till I'm ready to assume the task at hand.

The only real frustrating part is when some repairs fail, and need redoing