EV-reducing berries?

So I have this shiny Sandslash that I was very lucky to come across. I was very excited and trained it a few levels, but now I've learned that I can find my Secret ID from a shiny pokemon's EVs. That's true, right? And I could use that for RNG abuse to breed for IVs and shiny eggs?

I've also heard of EV-reducing berries. Which berries are these? How do they work? How can I get them? How many would I need?

Any help very much appreciated

Here's the sandslash if it's of any help.


RED TOPAZ Lv 33
Met at lv 28.
Quiet nature. Often lost in thought.
HP 99
Atk 72
Def 83
SpA 47
SpD 50
Spd 49

Pomeg=HP
Kelpsy=Attack
Qualot=Defense
Hondew=Special Attack
Grepa=Special Defense
Tamoto=Speed

And since the question has been answered *locked*

I'm going to sneak in a continuation of the question, since it wasn't thoroughly answered, and because I can.

The berries are numbered 21-26, and if you're playing in HG/SS, I believe the only way to obtain them originally is from your mother. They reduce 10 EVs at a time, unless you have more than 100 EVs in a certain stat. If it is ANY number between 101-255, it will (no matter the difference, can't stress it enough) reduce your EVs in that stat to 100. So the maximum number you will need for each stat is 11 berries.
Yes, there is a way to find your SID now, but it will take a lot of math or downloading a program. You'll also want to have all of the pokemon's EVs put to zero. The program should be called RNG Reporter, I believe.