I saw it was possible to open a video in Photoshop and edit it. I successfully cut out the background of my video on a single frame, using the magic wand. Is it possible to apply the wand on the whole video, selecting the same range of colors on each one of the frames? The idea would be to produce a chroma key effect (green-screening).
You can chroma key in Photoshop two ways; a good way and a bad way.
The good way is to use the Blend If command and do it by a channel (I'd recommend a or b channels, if you have a green or blue background, rather than the B or G channels). The bad way is laborious and inefficient, but is the one everyone recommends on the internet (making a selection).
There is one catch, though; buying After Effects or a similar programme will give you "feathering" for chroma keying. If PS had this one simple feature in the Blend If, then it would be *better* at chroma key than anything else, because you could use any channel you wanted.
Anyway, to answer your question, you use Blend If. The quality will be OK, but not be "pro" level because there is no feathering. (Adobe includes feathering everywhere, but there).