It will take longer via the Plot menu transparency box however, especially in larger and more complex drawings.  So this is where John's suggestion to use a custom Plot Style and screened colors may end up being faster and more efficient.  But both ideas work.

AutoCAD usually gives us many ways of doing the same thing.  I like to keep things as simple as I can so I don't lose time months or years later trying to figure out what I did.  And at that I still usually fail pretty miserably! 

Dave.