How should I EV my ferrothorn for competitive?

[jujii]

I have never played competitive before but have started teambuilding. Currently, my team is:

• Milotic - Bold
• Haxorus - Adamant/Zoroark - Timid
• Lucario - Timid
• Volcarona -Timid
• Chandelure -Timid

I looked through some competitive guides suggesting a safe playstyle would be to have 2 walls for a team, so I chose a Relaxed nature ferrothorn. However, I don't know how to ev it. Should it be 252 HP with 252 defense or special defense? Is a mixed ev spread a bad idea.

 

Since I have 2 fire types, Ideally I want it to tank water attacks, as well as psychic for lucario. Any help would be greatly appreciated!