A really good pokemon to use is a grotle it is a monster at walling
Grotle
Item eviolite
Ability Shell armor
Nature Careful
EVs HP 252 DEF 128 SPDEF 128
Stockpile
Leech Seed
Synthesis
Seed Bomb/Toxic
With the Eviolite his def is +300 and spdef is +320 one stockpile puts it at +400 with big...