Re: fireforming cases.
I fireform all my brass before loading for accuracy. I do this because I neck size for the most part and it gives me a better case/chamber fit. If you plan on FL sizing, just run them through your die now and have at it. If the brass and other components are from the same lot as used before, accuracy should be as expected.
Of course, testing the final product is always a good idea.
An easy way to form brass is to use Cream of Wheat (COW) or cornmeal over a light charge of pistol/shotgun powder.
You don't waste a bullet nor wear your barrel excessively. Helps you get rid of all those old or mystery primers too.