Transparent fill for Photoshop vector shape

For transparency you need to

• Open up the JPEG
• Double-click the background layer to make it a regular layer (background layers always have a background color I think)
• Use the eraser or whatever to remove the parts you don't want in the picture. To remove white, I would probably try to use the Wand or channels or something like that.
• Save it in a format which supports transparency (for example PNG)

The simplest solution would be to use a mask, but that would require you to remember to make the mask just before you export.

If you want to go this route, select layer 3, and then ctrl for windows/or command for mac click the layer you want to be the basis for the transparency, and then click on the icon down the bottom of the layers panel with the circle in a square. This will give you the transparency you want, but it's entirely manual and you have to remember to update it when you edit the black layer.

You could create an action that selects the layer you want to use and makes a mask from that, but you'd still have to remember to run the action...