I got mine off amazon I'm in Ontario smells terrible a small bit goes a long way. Soap is to kill neem to prevent 2drops neem 5ml of the soap I listed above in quart of water you're laughing. If it comes back you can reapply after 10 days DO NOT SPRAY IN DIRECT Sun. Also spray enough to get the leaf wet totally but not dripping do both under the leaf and top. I will also spray all surrounding areas and anti bug plants big help as well
Only method I've used sorry man don't know about the premix home hardware stuff I'm sure it works
Also leaf hoppers can be devistating they suck the sap out of new growths they don't bite but can transfer deseases with so many different breeds of leaf hoppers we are still discovery them today. Mainly you see in Ontario red stripes with green body's and they do have wings 6 legs.
I would suggest to read on leaf hoppers and prevention there are many different methods pick one that you think that suits you and when you find something that works and stick with it add it to your bag of tricks
NOW Neem Pure Oil, 30ml : Amazon.ca: Beauty & Personal Care
www.amazon.ca