Depends on the pesticide being used. Some are systemic, which means the pesticide is inside the plant tissue, and no amount of washing or soaking is going to remove any of it.
Many are oil based surfactants however, and if someone was using these late into flower, I suppose you might have a bit of luck washing these off. However, as anyone washing oily grease off their hands can attest, the stuff doesn't like to just "wash off."
Also... y'all are aware that Neem Oil is approved in Clean Green operations, correct? So not sure why buying clean green assures you that it won't have residual pesticides in it? There is no reassurance it wasn't used late into flower, and there are also organic fungicides that can and are used all the way up to harvest (Not that the bio-fungicides are dangerous to use in this manner anyways.)
If you are that concerned, you are looking for no-spray grows, which is becoming a thing...
