well silcoon and cascoon are easy to defeat and both give 2 points to defence, as well as aron's they are an easy target but only give 1 point, seedot id another, it gives 1 point
hope this helps
aron and lairon aron gives 1 and lairon gives 2 both found in the same cave so its good but put a macho brace on and if you can try to have pokerus on the pokemon also
If you have another GBA record mix with a team with only defense EV giving pokemon. Give your Chansey macho brace and it'll have max defence EVs in no time.