John, any "F8" filter will apply for LoTW export. Just select the prefix "!W" (exclamation point before the W) in your log (i.e. *not* W [USA]). This will give you DX QSOs only. Then do the upload flag thingie and you should be all set.
73 - Jim AD1C -- Jim Reisert AD1C, 7 Charlemont Court, North Chelmsford, MA 01863 USA +978-251-9933, [EMAIL PROTECTED], http://www.ad1c.us