1. Onion Skin gives you more control over the animation.
2. Create a new file. Create two layers. Draw the fixed objects on the bottom layer. And hammer which is movable on the top layer.
3. Insert 9 frames on the bottom layer. Convert hammer into symbol using F8. Edit the center of the hammer and bring it at the bottom using
Modify > Transform > Edit Center
4. Select top layer. Insert keyframe at 5. Bring the hammer down. Insert keyframe at 9 and drag the hammer back to original position.
Create motion Tween.
5. You will get the following output.
6. Select all the frames on the top layer and convert it into keyframes using
Modify > frames > Convert to keyframes
7. If you click on the Onion Skin (Red marked) You will get the positions of the frames filled with color
8. If you click on the Onion Skin Outlines(Red marked) You will get the positions of the frames with outlines without color.
9. Select each frame and edit using other frames as reference. In this project we have used Rotate command and changed the position of the frames using Onion Skin property.
10. Using Onion Skin, drag the first 3 frames very near to each other with rotate command. Compare the final output of the animation.
You will find the first animation is smooth one and the second begin slowly and increases the speed.
More Flash & Swish: 
