Blending Mode > Stencil Alpha
With Track Matte it is looking at the bottom layer.
But with Stencil it looks at all the layers.
Silhouette is the inverse
Color the paint trackmattes
Add a colored solid on top
Blending mode > Add
If you click the Preserve Transparency button (the box next to normal)
If there are layers with alpha channel bellow.
This checkered box button toggles the transparency.
Copying a shape from Illustrator:
Making a Mask in Illustrator
In Illustrator make a line with the pen tool.
Change the line so that it looks like it was made with a brush.
Object > expand appearance
Make a new solid and Ctrl+V
the line on top of the solid.
If the thing you pasted is jagged there will be a ton of masks.
You will have to go through the layers (the masks) to find the main object and delete most of them.
After you import the line from Illustrator
Effect> Generate > Write-On
You have to copy the mask path : the object>mask>mask path
Next, Ctrl+V on
Effects> Write-on > Brush Postion
If you have a very organic/painterly line
or if you have text like and 'e' where you get 2 masks.
After you paste it you can select all the masks and set the Mask Expansion from negative to positive and it will look like it grows.
To select multiple masks and make them appear:
When you paste the line and go to the masks in the layer they will all be selected.
Make a keyframe for mask expansion (they will be at 0, and each layer will receive a keyframe because they are all selected).
Then drag one of the keyframes over in the timeline.
Then make the mask expansion negative (but not more than -4).