You can find armors that have NoEncounters already on them, and you only need to have one character equipted with it to get the effect and you dont evan have to have that character in use. Thats an easier why.
And their weapons, they are very very good. Yuna's, when powered up,
Lets all the Aeons do over 9999 damage
Just to say, if you didnt know that...
And in getting their strongest weapons, its almost easier just to synth them up by using items and a weapon that has 4 empty slots. Thats what Im doing with Lulu's, getting her's is crazy.