As a machine quilter I spend a lot of time practicing and drawing out quilting design. I have used a variety of materials in the past to draw with before I found this App for my iPad.
I doodle ---a lot on my iPad screen using an App called Adobe Ideas. It is not a free App, and when I downloaded it over a year ago, the price was less than offered now. However they have upgraded it and you have the option of layers so I assume that is why the price has increased. It is a worthwhile purchase for $5.99 for your iPad if you love to sketch and practice your quilting designs before stepping up the to quilt as compared to using a dry erase board or sketchpad for example.
Adobe Idea uses the iPad screen as your drawing surface. You can use a finger tip to draw, but I prefer an iPad stylus. Either one works fine. You can pick colors of drawing pencils, erase and chose the size of pencil point. You can upload a picture of a whole quilt or a quilt block and draw over it. Save it. Email it to yourself, and print it out if need be. You can pan and zoom the drawing or picture. It's simply a lot of fun to use. Here is your iPad screen with Adobe Ideas and the drawing tools are on the left.
You have a blank slate to draw on. Pick a color to draw with and start drawing.
Here is a picture of a quilt I'm working on where I used some of the drawings I doodled in Adobe Ideas.