I use baby food jars or old glass jars or soup cans to decant spray paint or store it in.  I take a plastic sandwich bag and place it over the top of the can then spray into the soup can with the bag draped over the edge so that I don't get spray paint all over me and my hands or the surrounding area or overspray on anything else in my yard, or workspace. I then pour the paint into the jar or other things. I also mix paint with the soup cans. Just use your imagination when doing this. You'll be surprised at what you can think up when you need to!