I want to know how to breed to get a skrelp with acid armor
First you need you need to wait for the PokeBank/Transferer-thing to be released (Sorry!). Then you transfer a male, gen V Grimer/Muk with Acid Armor (Level-Up!). Breed the male Grimer/Muk with a female Shellos, until you get a male Shellos with Acid Armor. When you get the male Shellos with Acid Armor, breed it with a female Skrelp.
If you want to double check:
http://bulbapedia.bulbagarden.net/wiki/Grimer_(Pokémon)#By_leveling_up (Copy it)