Mor info on Rust Removal (Phosphoric acid)

I'd like some more info from those who've used Phosphoric acid to remove rust. I'm using Klean Strip Phosphoric Prep & Etch. Right now I'm trying it on a trailer. I applied some the other day with a brush to one fender and some other parts. Then a storm blew in. The next day a lot of it was white. I pressure washed the white off. When dry, a bit of white remained in places, a little bit was black and most was a light brown rust. Yesterday I applied more to about 1/2 the already treated parts. This morning much more is black but most is still light brown rust and it all has a glossy finish.

I'm not sure what to expect and what I can paint. Did I need to remove the white or just apply more over it? Do I keep applying until it's all black? Can I apply another coat over the gloss--or does the gloss lock in the rust and I should paint over the gloss?

Starting pics
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I didn't get a pic when it had all the white on it but here's some that remains in the bottom of the light housing
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after first coat and pressure washing to remove the white
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this morning after 2nd coat
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see the marks where the safety chains were laying on top and the glossy finish--it's not wet, it's glossy and dry.
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The trailer.
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All I can tell you is that when I worked on an offshore platform we used a chemical called Ospho by the gallon on all that saltwater rust. We never cleaned the white off. Just painted over it. Paint adhered without any problem. The white probably got mixed in with the paint. Your chemical may contain something that could cause an adhesion problem. Try it on a rusty piece of scrap and then paint over the white.

I have painted over it with no problems and have had problems with the paint coming off. I will admit to using cheap primer and that's never a good idea...

I would prep the treated surface by lightly scuffing it with a scotch bright pad then apply a good primer and paint...

That is to be a rust converter not a remover. Sold under lots of names. Duro extend is one.

I have tried it on cars and trucks for touch up and then top coated it and it rerusted just as fast as plain paint over rust.

Is the shinny rust good for paint now or do I keep re-applying till it's all black?

Yep, used to buy Ospho when I was on east coast, worked good aruond salt water. . Don't remember how t paint over it, but just follow the instructions.

I have used OSPHO often on surface rust. Paint right over it after it dries. Paint has always endured. I have a jungle jim wagner loader that I did that too 6,7 years ago. Paint still ok. I am in the process of doing a trailer's fenders. Should paint it tomorrow.