I remember doing finger paints with my oldest and he loved it. However, I would purchase the paints and by the end of one session he would have mixed them together or dumped them all out and they would be done after one time. This was certainly not cost-effective. Of course, the internet wasn't as cool as it is today and thankfully, there is access to all sorts of cool things online that helps us to save money while doing art with this kids. Now there are many ways to make paint but one of the easiest that we found simply mixing corn starch and warm water on the stove.
1 Cup Water
1/2 Cup Cornstarch
Heat on the stove on medium until consistency is 'paintlike' This recipe will make about 4 cups of paint.
You can crunch up the art when you are done and it comes out in crinkles like this. We have hung them on the sliding glass door and it adds a nice ambiance to the room. We also have another which was blue and pink. They came out really cute.