Anyone know how to buffer

you know i been playing alpha 1 and 2 and i just can’t seem to get the buffering concept down i am not sure how to do it:
example:
i am playing alpha 1 with ryu and i got somebody in the corner i sweep the opponent which knocks him down while he’s on the ground i do half the shinku hadoken motion the when charicter is finshed waking up i try to get him with C.lk + C.lk +C.mk then the rest of the lvl 3 shinku hadoken motion but the thing is i get the C.lk + C.lk + C.mk but not the lvl 3 shinku hadoken