I have read lots about neem oil but have never used it. I thought it was used if you have a bug problem like aphids. For some people it works, for others it doesn't.
I have used peroxide, pouring it on the plant where there was a problem and soaking the roots. I can say that every time I have used it on roots that the fizzing never stopped. So that may not be the best judgement on when it's been soaked enough.
I think physan has also been used as a preventive measure. But don't hold me to that.
You may need to soak the new medium (if it's bark) before using.
A dishsoap mixture is also used to treat bugs from what I've read.
Somebody with more experience will come along with better advice.
ETA: just saw the other thread with all the replies