How do you define "easy" and "quick"?
Here are two options:
Option1
Just drag the files from the Finder directly onto the Woskspace in GarageBand. You can drag the files onto an Existing Track Lane, to below, over the empty space of the Workspace and GarageBand creates new Track(s) for those files.
Option 2
If you have a specific folder with Media Files that you often need to import into your GarageBand Projects, just drag that Folder onto the upper area of the Media Browser. A new item with the name "Folders" will be created and any file/folder in that folder on your hard drive will be displayed under that "Folder" item. You can even add more folders form the Finder to that "folder" item (by dragging over it) and they all will be displayed in one convenient place. Just drag those media files from the Media Browser directly onto the Track Lane
I explain that procedure in my Logic Article, but it is the same behavior in GarageBand: http://logicprogem.com/LogicProGEM/Blog/Entries/2014/5/31_Media_Browser__Super_B rowsing_Power_with_Hidden_Secrets.html
Hope that helps
Edgar Rothermich - LogicProGEM.com
(Author of the "Graphically Enhanced Manuals")
http://DingDingMusic.com/Manuals/
'I may receive some form of compensation, financial or otherwise, from my recommendation or link.'