Hi Jakob,
These are two very different things.
"Resource Pool" in mS project is a separate file from which a project file
takes resoruces.
Each project can have only one resource pool (or none, when it handles its
own resoruces).
On the othe rhand, assignoing more than one resource to a task is easy and
can be achieved through several techniques, for instance:
- Task Information, Resources pad, enter on the different lines
- Click the Assign Resources button on the toolbar, slect the resources,
assign
How duration will react when you assign more than one resoruce to a task is
too long to explain here.
You could look up the item in any book on Project, or in the series of
articles published by fellw MVP Mike Glen, at
http://tinyurl.com/2xbhc
Hope this helps,