WoB (White on Black) is a fast drawing app for the iPad, iPhone and iPod Touch.
It now has a special designed brush sizer / selector. Tab to switch to white or black and hold or slide will make the slider for the size show up.
And it has a drawing library.
Swipe down 2 fingers will reveal the library.
Tab a drawing to load it.
To delete or duplicate a drawing, hold down your finger on a target drawing.
Locking the drawing will avoid you from destroying it and avoids the sleepmode while showing your drawing to someone.