Dont see whats hard about this?
Setup a 2 player local game, pick Ryu VS Sagat, then do the move to finish him, it unlocks, easy.
Press forward, then slide your thumb through to down, then slide to forward down, and hit HP, must be HP.
It WILL unlock, if not then your doing it wrong.
And if anyone cant do a Shoryuken, then good luck with combomaniac lol