I haven't use these yet. But, they are merrily sitting in my Freezer just waiting for the right time. I just added a touch of liquid watercolor to some water in a ice tray and mixed it up.
I've heard that they are fun for kiddos to play with on a stretched out piece of cotton. A fun way to paint. I'm thinking of cutting up one of Papa Bear's old under-shirts and giving it a try on a hot, sunny day.
I'll let you know how it goes!