This seems like such a simple question that I wonder if I'm reading it wrong and missing a much deeper question :-)
Let's say you have some task ("Dig a big hole") that you estimate will take 12 days of effort for 1 person working 100%, 8 hours per day (96 hours total). You assign your best worker, good old Resource 1:
You need the hole completed sooner, so let's get Resource 2 on the job as well. Just click the Assignment button in the toolbar and check Resource 2 while leaving Resource 1 checked:
(I turned on the Duration column also via View->View Options...)
Both resources are working at 100%. Let's throw Resource 3 into the mix:
That's still not quite soon enough, so we'll toss in Resource 4, but we can only afford to allocation 50% of his time:
I assigned Resource 4 in the same manner as the others, then used the inspector to edit the percentage assigned to this task.
Each full day 8+8+8+4 hours of effort will be expended on this task, and the task will be complete in just under 3 1/2 days.
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