Rear Shock question

[250rmanfmf]

I a lot of perfectly working rear shocks that I want to polish the tubes on them so I have to take the coil spring and disconnect the line. Now what do I do to put it back together as far as a charge, how much fluid, and then do I just add a certain amount of PSI, or do I have to take it in a get it nitrogren charged? need help

Thanks

[asc180]

if you take it apart you destroy the seal in the bottom. you have to have them filled with nitrogen.