There are probly a total of 8 rare candies in Pokemon platinum
Buy an action replay and set it to 999 rare candies
on the ground
If you want tonnes of rare candies, I suggest you save up your money to buy gameshark or action replay ds/gameboy advance to hack the game and get extra rare candies.
999 rare candies on platinum 94000130 fcff0000 b21c4d28 00000000 b0000004 00000000 00000dac 03e70032 d2000000 00000000 (only wrks w/action replay)
You get ye a million rare candies and two Arceus.