If you remove the locks to have the handles powder coated, I'd suggest using
carburetor cleaner to remove all the grease inside the handle's lock
housing.  Also clean the lock plug (guts of the lock) with carb cleaner.  Be
careful, and keep a key in the lock, or the wafers will fall out after you
clean the lock.  Plug the hole in the handle so it is not powdercoated
during the procedure.  Ask the powdercoat shop about their preferred method
of masking the hole.  To reassemble the locks, lubricate with a teflon or
silicone based lubricant.  Tri-Flow works well.  Do not use grease or WD40.
Hope this helps somebody.
Steve Sandlin      www.steveslockshop.com
'84 Wolfsburg Westy
'79 Transporter
"00 New Beetle