So it's not actually fire scale that I am having the problem with. It's called fire stain. Fire scale is the oxidation you can remove after firing by sitting in it pickle until the fine silver comes to the surface.
In the picture to the left is what fire stain is. Once you have done all your sanding and your polishing and you have a funny dull grey colour on your metal (even though it's shiny). The only way to remove the fire stain (not in all cases), is to redo all the final sanding and polishing. If it is removed then you know it was only surface fire stain. But if it's still there, you may be able to repeat the whole process again and have some success or you may never get it off. Then you can look at possibilities of either plating the item to cover up the fire stain or you can choose a different finish like oxidization or a brushed finish.
I am scrapping this ring. I am not happy with how the bezel turned out. So I might see if I can remove the fire stain for practice. My other ring that I finished had fire stain too. Lots on the back and some on the ring shank. I tried a couple of times to remove it and it's come away from the ring shank, but the back still had some, so I have chosen to put a brushed finish on the back only and the rest I polished up.
I emailed the company that advertised it had some Prips Flux, but they wrote back and said they don't actually stock it and they have Fire Scoff instead. So my only option is to make up my own Prips or a boric acid and denatured alcohol mix, which apparently works really well too. So anyways, I don't want to make anymore jewelry until I can come up with something to prevent fire stain. And I have an order of some nice silver coming in the next couple of days....so I hope to mix something up by then.