Fluke I can't think of a way to do it other than with arbitrary code execution. The easiest way is using glitch item 8F:
http://forums.glitchcity.info/index.php?topic=6638.0. Use the first method to obtain 8F which is by far the easiest. To get 255 x specials, put X Special x1 in the sixth position of your bag, then encounter MissingNo in cinnabar via de old man glitch. You'll have 129 x specials now, so toss two and then encounter missingno, to get finally 255 x specials.
Then arrange your party the way it says under "bootstrapping". You may notice at this point that setting up 8F could be even more time consuming than ev training your pokemon (unless you want to ev train multiple pokemon of course), so it's up to you if you still want to do it this way. (to get the 233 atk pokemon I suggest you clone a bunch of rare candies with missingno and then give them to something like gyarados; if you can't make it hit exactly 233, then reset and try again with another pokemon).
Finally you have to spell out a code that replaces the ten EV addresses of your first current box pokemon with the value 255. If everything went well the game will be executing assembly code from address D322, which is the third item in your bag. So you can rearrange your items with something like this (starting from item 3; items 1 and 2 don't matter):
Thunderstone x167
TM18 x175
Soda Pop x15
Moon Stone x34
Ice Heal x5
Fire Stone x251
TM01 x1
In assembly:
Code:
ld hl, $daa7
xor a
dec a
ld c, 10
.loop
ld [hli], a
dec c
jr nz, .loop
ret
To get 2-127 stacks of an item, you may put that item (x1) in the 6th slot, encounter missingno, then toss until you have the number you want
To get 128-255 stacks of an item, you may put that item (x1) in the 6th slot, encounter missingno, then toss until you have 127, encounter missingno again, then toss until you have the number you want.
For quantities over 100 the first digit would be 10-25. That's how these digits are represented when inside a Pokemon center:
If you don't mind (or want to) replace your Pokemon DVs with $ff (all 15), then replace Moon Stone x34 with Burn Heal x34
I just put this together hopefully there's no bug in the code.