Ah, well here's part of the problem. I'm clipping MKVs, which Streamclip, or rather my version of it, doesn't love. So there is no audio because it doesn't work for some reason. And the conversion is very slow, and the computer gets stuck sometimes if I skip around. (I can jump from one section of the episode OK, but skipping around within a scene makes the video freeze momentarily.) High speed isn't an option. All of these things slow me down. Even not having sound, because I'm rewatching as well -- I don't remember the show well enough to clip from memory this way. So I rewatch on VLC, take notes of what scenes to clip, and then open the episode in Streamclip.

But when I've clipped MOV or MP4 files, I guess it depends? If it's a source I know well, like Buffy, I definitely turn off the sound, watch at 2x speed, and skip scenes. When I was clipping for my tightpresent vid (sob!) I watched with audio on and at 1x speed because I wanted to re-watch scenes. But I did skip scenes that weren't relevant to the vid I was planning.