Basically who in Naruto have we seen use Kage Bunshin. I've seen Jiraiya use it when training his pupils. Naruto uses it occasionally (lol). Kakashi has used it. As fas as I'm aware I haven't actually seen Sasuke use it (He uses genjutsu against Itachi, and Itachi in turn uses genjutsu). I have seen Third hokage use it.
Orichimaru does not use it. What he does use is an earth based element jutsu that molds mud into a bunshin. So, are there any others who have used Kage Bunshin.
As far as I'm aware its a forbidden technique. I doubt it isn't because I am assuming that in order to use mass shadow clone jutsu, all you do is use the kage Bunshin technique simply diving your chakra into more clones.
Now mass shadow technique is forbidden because its spreads out the chakra of the user too much.
If mass shadow technique is a secret forbidden jutsu, then the normal Kage Bunshi must also be a secret technique because if you know how to do normal Kage Bunshin, then all you do is divide chakra into more clones to create a mass shadow clone technique.
Therefore If you knew how to do Kage bunshin, then you would know how to create mass clones. You may run out of chakra and die (which is the whole point of it being forbidden) but would know how to create mass shadow clones.
With that said even a normal Kage Bunshin must be a secret, forbidden technique. If not, then it would be a huge gaping plot hole on Kishi's part because how can you keep mass cloning Jutsu as a secret, forbidden technique without also doing the same for Kage Bunshin.