You may also want to glue a photo of your child to the front of the bottle. You can explain to your child that this is his own personalized protection against the bad guys and that he needs his own personal shield on the bottle for it to work. In reality, it's a way to help your child to recognize his bottle, even if there are other spray bottles around the house.
(Please note that I've tried smaller sized bottles and while they should work the same way, they don't seem to. The size and weight of the larger bottle seems to make it a more viable "weapon" to scare those monsters away. It is important to check the nozzle thoroughly and remove any small parts that could be a choking hazard.)
It is then presented to the child with a flourish and ceremony of your own creation, along with instructions to spray it on the monsters to make them disappear.
Your child can actually sleep with this bottle or you can remove it after they have fallen asleep. Either way, just feeling that they are in control of a powerful "weapon" can be enough to eliminate the monsters entirely. Try it tonight and see for yourself. Here's wishing you a good night!