I still use the "object name separator" script Michael wrote here:

http://moi3d.com/forum/messages.php?webtag=MOI&msg=3114.1

The script is in post #5 and you need to have your object boolean unioned and
other elements of the object can be isolated with styles.

If you leave your objects unnamed, they will also get auto numbered at export time with names like object1 object2 object3, etc... for each different object.

- Michael