questions: sealing/painting old tin roof

Our old tin roof has gotten pretty rusty but we can't afford to replace it yet. It only has patches of silver paint left on it.
We've been told to get as much rust off as possible with a wire brush. Is there any more thorough or faster method? BTW, we live in Louisiana, so during the project we may be stopped by rain more than once and have a wet roof to boot. Should we try to cover it? (The humidity is such here that I don't know if there is a way to keep it dry until primed.)
Anyway, after steel brushing or whatever we need to wash off the residue. Is trisodium phosphate best for this or should we use some solvent like mineral spirits? Can we sandblast instead of the steel brush?
I figure during this we may find/create places that might need patching, so any advice on that is welcome. Would a sealer go under or over the primer, or would the primer act as a seal?
What is the best kind of primer for the job? (I'm assuming some remnants of rust will remain)
What is the right kind of paint? Someone told use latex, and we had ever dreamed of latex on metal. I want it painted an earthen color like terra cotta, and I've been told that earthen colors paints last longer because of the minerals used to make the natural colors, is this true? Is there an acrylic/latex paint specifically for roofs?
We are also curious about the notion of flipping the panels. We can see most of the downside of the panels from our attic since there is no underlayment and haven't found any rust so far. But, if we were to flip the panels wouldn't we still have to clean and prime the rusted outside first before flipping?... Then still shouldn't we prime and paint the outside?
Lastly, we have little to anchor to for safety's sake. An old chimney is about it, and uneven ground to support the ladder. The roof doesn't have a solid underlayment, so we figured to stand or sit on large pieces of thin plywood to distribute our weight. Any logistical and safety tips we can pick up would be most appreciated. We're both in our 50's, and I get vertigo, so most of this falls on my husband's shoulder. He's got a week in March to get the worst of it done.
Thanks for any help, inez
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You might ask your paint dealer for a special rust paint that bonds and mixes with the rust and converts it to a black glossy primer. I've used this to check rust on garage freezer, and car dings. It requires little prep or wirebrushing. Then you could spray prime it - metal prime - if you are anal - , or, if the surface is sufficiently rough after the special prime, put an acrylic latex exterior paint topcoat on it. Yes, latex, if high quality, will last longer than oil, if it is properly primed beforehand. They also have primers especially for zinc plated (galvanized) roofs like what you have, but may require more wire brushing at the outset. Again, latex can be used as a topcoat.

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I wouldnt use House paint and regular Latex Breathes, it wont provide a good deterant against moisture- rust. Look into commercial products from Sherwin Williams, such as 2 part catalyzed epoxy for Water storage tanks. Talk to Paint Cos, such as Sherwin Williams, Benjamin Moore, and commercial industrial painters. You have big job, do it wrong it will be a waiste. Do it right , it will be the best you could do. Its realy not a homeowners job.
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