coatings and treatments

[kfcpork]

so after stumbling threw the resurface/re hardening thread it made me realize im still very very dumb. anyone want to give me an explanation on why you nitrate plates when reconditioning them? also would it be a good idea to do the same to rotors?!? what about cryo-ing (crap grammar i know) plates and rotors or shot peening/wpc treating them?!? has anyone on here tried any of that with good results or cryo-ed seals or even wpc treated them?!? any clearance issues afterwards? food for thought i guess after i saw the re hardening thread it made me wonder so seeing what you guys think/know what works and doesn't