With leftovers, I keep them in bottles clearly labled and shake them when needed and use(neem oil). (I use bottles that Shane is unfamiliar with and tell him they are poison--I use red marker so he sees the difference). I have only used an aresole can for fungicide so far. AS far as the actual containers they come in-- I rinse them well and put them in with the recycle bin. They
(recyclers) always take them.