Yes, with 400 machines that would prove to be very difficult and time consuming. Most organizations with this many machines are usually set up on a domain controller (on a Domain) where user rights can be changed at the drop of a hat.
If you're set up as a workgroup with 400 machines and the logins/passwords are different, even a feature that allows different logins/passwords may not be practical because you'd need to type in a username/password for each machine at least once.
The only other choice is to use an agent, which you would need to manually install on each machine, or by installing it remotely by typing in each machine's username & password as it is asked. This could take hours or days to deploy. Our software lacks this feature at this time, but it is being developed.
I'm sorry we couldn't be of any more assistance. We would ask that you check back in the future to see what developments we've made.
If you have any more questions, we'll try our best to answer them.