Leftover cans from formula or snack: These cans are cardboard with a plastic lid for resealing and have a metal bottom. Save the lids someplace cause you can use these cans over and over for dry snacks, toys, etc...
Paint: Use any kind of craft paint. The darker the color the easier it will cover any words on the cans. The liquitex paint is actually an acrylic art paint. More expensive per tube but awesome coverage.
paintbrush: Use a wide brush. Covers faster and easier and your done that much faster.
fine grit sandpaper (this is for the slick silver cans. These are the coffee cans and the toddler transition formula. Basically if the can under the wrapper is silver, your gonna have to sand it otherwise the paint will NOT stick to the can. And yes I found that out the hard way so you don't have to!)
Here's the final result. I haven't gotten all of them painted, as you can see, but I did get some of them. We play games. I hide toys in the cans and I ask them to bring me whichever color can. They are young but its a start on color identification. We also flip them over and use them as drums! Music appreciation! They also enjoy turning them over and banging them on the floor. I have herd so much squealing and laughter over these cans. I love it! And at the end of the day I just make a pyramid out of them and tuck them in a low traffic spot.