No, the IV thing depends on your timing with pressing buttens (not difficult) and the Timer0 (luck).
Advancing the PID frame, the Chatot thing, is required for nature, gender, ability, encounter slot, and shininess; in your case, only nature and shininess.
What you have given us is not the seed. The seed is that long string of numbers and characters. 124 is your Target frame, 49 is your starting/initial frame, and 75 is the difference/number of Chatot flips.
When the IVs (and consecutively your nature and shininess) are not correct, you have hit the wrong seed. As said, it depends on your timing and your Timer0. When you play BW, it is most likely an issue of timing, because the Timer0 does not fluctuate that much. When you play BW2, it might be one of them, or both.
If you think your timing is off, just calibrate and look at the actual second. It indicates how long it took for the DS to boot the game and you have to adapt to the slight delay.
If you think your Timer0 is off (means: bad luck), try again until you get the correct result.
There is actually a third option we haven't mentioned yet because we have expected you to do it correctly. You need a custom Chatot chatter to advance the PID frame. The default one does nothing.