the Faq has all the answers you need... all we can do is reafirm what the faq says.....
You can use any rod, the only difference between them is what you catch, magikarp and tantacool on the old rod, carvana on the super, both catch feebas.
there are 6 tiles that feebas is located on... THEY ARE COMPLETELY RANDOM
you have to search for one of those tiles. Don't listen to anyone that says that they found it on such and such tile with such and such phrase because it's STILL RANDOM. just search in the water on the route where the weather institute is... search each tile about 3-4 times.
SEARCH SEARCH SEARCH that's all you can do.