Does anyone know what action it is issue commands to undead you control or just took control of? I was thinking either free (talking) or move as per handle animal. Thoughts?
Well, the command undead spell heavily implies verbal commands, so almost certainly a free action.
The command undead feat says it works like control undead, which specifies language as the basis for commands, so again a free action.
The animate dead spell is completely silent on the matter. Given that all the other major methods are all verbal, I suspect this one is as well, so free action.
Since the communication is mostly effectively verbal, the time required is contingent on the complexity of the action you are requesting it take. I would say most would fall into the category of "free action", but at DM discretion exceptionally complicated commands (i.e, the sort that could only be given to intelligent undead) could possibly require longer.