For me it was a bit hard because I live in a tiny apartment and this is bound to be messy. So on one of the last sunny days of the year I just tossed some supplies off the balcony and painted my sheet in the grassy area there. It was hard because it is a public area and I never painted in a public area. But in the end I had a lot of fun experimenting. It is all about using your paints mixed with different amounts of water so you can toss or drip the paint. Here is my sheet (still wet) in different angles.
Luckily it was a quiet day and I didn't really encounter people. Only a dog and of course my own cats who came down to see what for silly thing I was doing. I can see myself tossing some paint around more often, only not likely on a sheet again, because I have no idea what to do with it now ;)