Migrate from OS X 10.9 back to 10.8.5
The easiest way would be do a Time Machine backup of your 10.9 Home and Applications folders only.

Then do a clean install of 10.8.5 and boot up in recovery mode and restore your 10.9 Home folder, and pick which applications you wish to restore from your 10.9 Applications folder.

I've had to do this rolling back to previous OS X versions and have rarely had too many problems.