In Pokemon Pearl, what's the best way to max out a Pokemon's beauty stat?

Question

Obviously, I'm doing this to get a Milotic.

I pretty much have all the berries, so I'd like to know specifics on which ones to use in poffins.

Answer 1

The best way is to feed it dry poffins that help increase it's beauty.  The following berries are those that will increase beauty, and their base increaser.  

Chesto 10

Oran  10

Persim 10

Lum 10

Sitrus 10

Wiki 15

Razz 10

Bluk 10

Kelpsy 10

Hondew 10

Grepa 10

Tamato 10

Cornn 20

Spelon 10

Pamtre 30

Passho 15

Yache 10

Kebia 15

Coba 10

Charti 20

Kasib 10

Chilan 25

Liechi 10

Ganlon 30

Apicot 30

Lansat 10

Starf 10

Enigma 10

Micle 40

A Pokemon's nature can also affect the beauty it gains.   Modest, quiet, Rash, and Mild  natures will increase the value from the dry poffins, and Adamant, Jolly, Careful, and Impish will decrease the value from dry poffins.  

Also, once your Pokemon gets 200 beauty points, you can get a blue scarf from the scarf guy in Pastoria city that will increase it even more.

Answer 2

I'm not too knowledgable about the berries, but I do know that dressing up your Pokemon with accessories. I believe that'll raise your Pokemon's beauty stat.