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I use aliases........

Didn't have a capacity issue due to the smaller quantities of media that I have but in order to keep organised I have just set up aliases to point to alternative drives i.e Within my iTunes Library on drive 'a', Movies are aliased to drive 'b'.

Really simple and works perfectly. :)
 
I fill one up and move on. I change the copy preference under advance settings then just drag and drop. iTunes will remember the path
 
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