That's my plan, I'm hoping that the parts under the coating are suitable for rust bluing. If not, new parts.You don't have to 'strip' anything. Carefully sand the part to get the finish you want, which of course removes the Phosphate along with the blasted surface. Then start your rust bluing process.
IIRC, I used Muriatic acid when I epoxied my garage floor, to etch the surface. Yes, it's dangerous but reasonable care will mitigate most of the danger.I removed mine using muratic acid. Hone depot or lowes in the paint section. Comes in a gallon.
Wear eye, hand, arm protection. Etc etc.
If your using it and don't know how dangerous the stuff could be, don't use it.