You
can reuse masks in other layers and compositions—particularly Bezier
masks you’ve spent a long time perfecting. Mask paths are stored
inside a composition in a project file. It can be useful to create
a project with compositions just for storing complex layer masks.
When you want to use a mask from another project, import that project
into your current project.
Open the composition containing the mask you want
to reuse. If you saved the mask in another project, import the project
and then open the mask’s composition.
In the Timeline panel, expand the saved mask’s layer
and mask properties.
Select the mask or keyframes.
Copy the mask or keyframes, and paste the mask or keyframes
to the layer to which you want to apply the mask.