Instructions
Battle Frontier
Head to the Battle Zone and enter the Battle Frontier areas.
Play through each challenge area and beat all trainers. As you do so, you will amass "BP," a currency exclusive to the Battle Frontier.
Head to the Exchange Service Counter in the center of the Battle Frontier once you have completed all challenges at least once.
Purchase as much Rare Candy as you can with your BP. Each Rare Candy costs 48 BP, so you may only be able to buy a limited quantity.
Repeat as necessary. Battle Frontier challenges can be repeated for more BP, making it an excellent place to get large quantities of Rare Candy.
Pokemon Mansion
Travel to Route 212 and head into the Pokemon Mansion.
Accept and complete the "Five-Maid Knockout Exact-Turn Attack Challenge." This challenge requires you to defeat five maids in Pokemon battles in a specific number of turns and may require some practice to perfect.
Accept the challenge of Lady Celeste or Rich Boy Liam at the end of the "Five-Maid Knockout Exact-Turn Attack Challenge."
Use "Trick" to steal a Rare Candy from either Celeste or Liam's Blissey. Your lead Pokemon will need to know this move and will need to be extremely fast; otherwise, Blissey will use the Rare Candy as a weapon, employing the "Fling" move and rendering it impossible to steal.
Repeat as necessary. This challenge can only be completed once per day, but it is available every day for another virtually limitless source of Rare Candy.
Pickup Ability
Create a party of six Pokemon who know the ability "Pickup." Make sure none of these Pokemon are holding items.
Engage in as many battles as possible. For optimum results, handle the battles at Pokemon Mansion and the Battle Frontier.
Check your Pokemon's status after each battle and remove any items that accumulate. Pickup grants a chance to pick up an item after battle but only if the Pokemon isn't holding anything.