A good way to nail the timing to begin with is to press the button while you're in the down portion of the croush dash. By the time your hand rolls to the down/forward the button press should match up for the just frame. On 2P it's almost too easy to roll through the crouch dash motion so the timing may be slightly different for you. Go slow with it and focus on accurately doing it many times consecutively, then speed it up.
If you're using Kazuya it's important to mention that he has a shortcut option of f,n,d/f that makes it a bit more lenient to execute, but if you're solely practicing with him you may lean on that too heavily. I'd suggest practicing with either Heihachi or Devil Jin (unless you just plan on using Kazuya all the time forever, then do as you please).
It takes tons of practice and patience to really get this down pat (more than I'm personally willing to commit ATM), so just be prepared for that monotony. Once you feel really comfortable doing it, then comes the greater challenge of using it in actual matches, a whole other beast.
