No big deal.
-Lube case, run it through a FL .308Win die without the expander ball.
-Anneal case neck
-Run the case through a .260Rem die. (You can run it through a 7mm die first, to minimize any case losses)
-Neck turn
-Trim as necessary
Is it worth it? Depends on how much your time is worth and how hard it is to get correct 260Rem brass. Easier if you start with 7mm-08 or .243Win brass.. One step either way.