I have recently got Facebook to work when debugging my application by following the insructions on facebooks developer page on how to export and get the hash key we need to
You are correct on the key hash's being different from the debug.keystore and the release signing key. To remedy that, follow the steps on this website here: http://www.helloandroid.com/tutorials/using-facebook-sdk-android-development-part-1
It has a nice tutorial that will fix the issue in almost no time.
The gist of it is:
C:\Program Files\Java\jre7\bin
openssl sha1 -binary debug.txt > debug_sha.txt
And then,
openssl base64 -in debug_sha.txt > debug_base64.txt
Done! The debug_base64.txt contains your Key Hash. Copy this in your app console and you are all set.
This sounds lengthy, but you really will be done in literally 4 - 5 minutes. ;-)