1. To import a PS file into after effects, you click the file one, and then you import as composition.
2. If you choose composition from the import then you will bring it the layers in the right order and size. Composition cropped layers will bring the layers at the size of every layer, not the document. Footage will allow you to merge layers, you can bring in only 1 layer if you want.
3. After effects will recognize layers, visibility, opacity, layer blend modes, alpha channels, layer masks, and adjustment layers.
4. To apply layer styles in after effects, R-click, then go to layer styles.
5. To make text layers coming from PS editable in after effects, go to layer, and select make editable text.
6. To export a frame as a layered PS file, go to composition, go to save frame as, and then PS layers.
7. Some creative things you can do going between after effects and PS are, is making the layers more fixed with photoshop.
