Heres how I look at it ...
Theres absolutely no doubt that Ospho does a few things very well..
1) it removes rust
2) it protects bare metal from surface rust for many month while your getting ready to prime...
3) on good unrusted metal it cleans and etches
metal preps and conditioners got a bad rap so everyone just bunches them all up into a pile and says DONT USE THEM...I gotta admit these guys had me going and doubting myself ,maybe they were right ,so I did every kind of test I could think up and some that some others thought up then I did some test like the government does.In every single case my treated metal held the epoxy as good or better than metal that was just sanded and primed.If anyone can show me a problem ,Im all ears,but all anyone ever says is so and so dont recommend it or I'd rather prime rust or just prime right over the flash rust...I'm not saying its fool proof but it is pretty simple to use what I'm saying is:if you cant blast your rust this WILL work well too. even if you bring your car to a media blaster it'll have surface rust before you can prime it Ospho will protect it untill you can prime.
So If You have any doubts about the adhesion of your epoxy why dont you just sand the ospho off one panel and prime that one panel then move to the next? it very easy to see what was sanded because it looks much much cleaner then when sanded off than untreated ,sanded metal....Consider the Ospho a cheap EZ to sand off way to protect your metal kinda like rattle can primer but ez to remove with some sanding..its a lot cheaper too 15.00 a qt
Not every car gets tore down and put on a rotiserry and in a booth either and thats the only way I'd media blast a car Ospho is just right for everything else...I'm not going anywhere ,if anyone has any trouble using it just say so Ill help you get it right....