Not worth it! Too difficult to place brushes in areas!

Is there a secret to erasing? I try erasing the an area, but the brush will erase a different area. When I undo, I have to reset the brush size, and then it will crash! I have not been able to finish one photo because it will crashes!

JDC Designz about Photo Eraser HD - Foto Editor To Erase & Remove Staples Backgrounds