There isn't a real good way to convince Rotary to choose your first choice besides putting it as your first choice. That's all they're looking at there. They will check into other things as well such as personal habits, age, etc, but the rest is up to your list. It's possible you will be placed somewhere that wasn't even on your list if you are in a competitive district.
The way that I learn kanji is repetition. I choose a set of around 10 kanji and I just mix them up and write them over and over again along with the yomigana and different meaning they can have. If you make it to Japan you can use the elementary school books. They are very helpful because they include grammar along with the kanji.
Good luck learning Japanese and figuring out an exchange!