Don't matter neither one will work - it's just to help emulsify this mix better.
I'm buying Oils from folks called "NOW" - really good shit for very good price. Also, Dr. Bronners castol peppermint soap is good to add to the mix, but only few drops per gallon of water - that stuff is strong as hell - and I would skip it for now and use oils only until you get comfy with a process.
Do it 3 times every 3 days with light clean water spray in between - you'll be clean enough to finish them with preventive spraying ones a week.
In your case by spraying I mean wiping leaves and stems - not spraying them all down soaking wet..
https://www.amazon.com/gp/product/B0013OXEFK/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1