Prometheanplanet makes using magic eraser a breeze. Download the magic eraser resource. The resource offers ready-made images that have the magic eraser build into them. The resource pack offers many images such as a magnifying glass, glasses, binoculars, and many more fun graphics.
Layering is the key to using the magic eraser. The image with magic eraser needs to be on the top. The image that covers what you want to reveal goes on the top layer just below the magic eraser. Revealing an item requires placement of that image on the middle layer. I would also recommend that you lock the magic eraser if you plan on moving items into the magic eraser like the example below.
Creating magic eraser tools from scratch is a snap with Activinspire. The Object Browser makes it easy to see the layers that objects are located. You can quickly move objects from one layer to the next. No more guess work like in Activstudio.
The best way to improve your skills with magic eraser is to dissect flipcharts containing magic erasers. There are many on Prometheanplanet. Have fun with the magic erasers.