Well, I already said that it required it to be cyprted, although you did read the man page, so that's a plus! :-)
Here's a sneaky tricky way to do it.
At the command prompt, type passwd Enter the password you want the other users to have. Look in /etc/shadow at what the newly crypted password is, copy the entire string ( of the password, not the entire /etc/shadow string for the user ), then type passwd again, change the password back to your old password, and you now have the crypted string in which to put with the -p option.
There may be some utility out there that gives you an md5 string/crypted/thing-a-ma-jig, but it's just as easy to do it the way I just suggested.