as far as cleaning up grain, random artifacts, ect, use avisynth as he said.
your friend may have been talking about stamping unwanted items out of the video, or color correction. both which can be done in after effects.
alot of people use avisynth for color correction too. i prefer having more of a visual aid like i would in after effects, premiere, ect.
KioAtWork: I'm so bored. I don't have class again for another half hour.
Minion: masturbate into someones desk and giggle about it for the remaining 28 minutes