Neem oil recipes for Aphids

Hello everyone! I have a small Aphids problem in my growbox. So far I could pick out almost all of them, but of course you can't really kill all just by squishing them. It's still quite early in the grow cycle and my plants are still a couple weeks away from flowering. I heard that Neem oil, combined with water and a little soap can help, but I'd like to know your advice and what recipes you guys use first. Thank you in advance!