Neem Oil

[MuddyBuckets]

Major aphid attack so I bought pure neem oil, mixed it with water and a bit of dishwashing soap as directed and put it into a spray bottle. My questions are 1) what is the best dishwashing soap to use, 2) would Murphy's Oil Soap be a good addition, 3) how often to spray the peppers, tomatoes, okra and eggplant, 4) should the neem spray be washed off after application and 5) how often to spray the plants.

Any ideas or suggestions appreciated.