Getting rid of Rust

Hey whats up fellas. I got a few questions that i need straightened up, so if anyone could help that would be awesome.
I am doing body work on a 68 dart, and i have sanded the metal down to strip out the rust. I have DX-579 to get rid of the rust, and DX -520 to put down a zinc layer , but i have a few other questions. On the inside floorboards, i need to get rid of the rust before i weld, i know the dx-520 creates a layer of zinc, which will make me sick if i weld it, but does dx-579 create a layer of zinc or no? Is it safe for me to weld after using dx-579?
Also, if i sand down areas that are not rusted out, can i just shoot it with self etching primer and then layer it with high build primer? or do i need to treat it first even though there isn't rust?
I figured i would get the help of someone who knows what they are doing before i go and get ahead of myself. Any info on it is greatly appreciated.