(My note - you could use permanent markers and make this a little bit easier in my opinion. You can get blank umbrellas at Dollar General, some Dollar Stores, Big Lots and Walmart fairly cheap.)
Here are the directions:
Coaxed open by raindrops, umbrellas bloom like flowers in spring. Your child can turn hers into the prettiest of them all by painting it with a fanciful pattern. It only takes a few supplies and a child-size umbrella. Give kids this absorbing activity, and on the next wet day, they can show off their handiwork in the rain.
Umbrella How-To
You will need a kid's nylon umbrella (paint won't stick to a plastic one), paintbrushes, and permanent waterproof paint, such as fabric paint or acrylic. Follow the manufacturer's directions: Some fabric paints require the addition of fixative; others require ironing the umbrella after painting. Carefully cover the work surface with newspaper before you begin, and have your child wear a smock. Once finished, keep the umbrella open overnight; the paint must dry completely before you close it or use it.