heh...
i actually beat both of them WITHOUT the Final Attack materia.
against emerald, i had all of them at 8500 hp or more, i had cloud w-summon KOTR (which was connected with HP absorb, so cloud gained 8000 hp when he used it), and Phoenix. then i had everyone mime (which was connected with Counter). i suppose it woulda been easier if i had cloud use omnislash at the begiinning and then use him to keep miming it.
against ruby, i had yuffie and vincent dead, and summoned phoenix right away. if any of the tentacles attacked and gave me statuses, i had cloud and vincent cure them. then i used yuffie to w-summon Hades and KOTR (since Hades parylyzes ruby and ruby can only be damaged by non-elemental summons, like the bahamuts and KOTR). then i mimed all the way.