The "unified" way of doing this is now lua, though some plugins have specific code to do this.
To set a discrete instance:
or, in one nice string:
plugin = NetRemote.GetPlugin('ZoomPlayer');
plugin_instance = plugin:GetInstance(instanceid);
note that GetInstance can use either the instance ID (as a number), or if the instance is "named" you can pass the name in.
Brian, you can have named instances by setting the variable "instance_name" in your instance.