This Plugin applies squash and stretch to an instance maintaining its volume. You can also view the amount of squash/stretch of a selected object.

Removing the Squash and Stretch

Open the Plugin by clicking Window/Other Panels/[T] Squash Stretch.
Select an object on the stage.
Press the button Remove Squash. This will remove the squash and stretch of the selected object.

Learn how to assign a hotkey to this button.

Applying Squash and Stretch

Select an object on the stage.
Move the knob up and down.
If you need precision, press the arrow buttons on the left. The small arrow will apply 0.25% and the big one will apply 1% of squash/stretch.

Learn how to assign a hotkey to this button.