Hi, welcome to Spine forum

It is a common case. Personally, I recommend that you do not separate images on an image editor, but use meshes on the Spine editor to separate them. I have answered a similar question before, so please refer to this post for detailed instructions:
Matching Clipping Mask deform to specific mesh deform?

I hope you find this helpful.

Regarding how to import additional images on your project, you don’t need to use the same psd. Images that are exported by PhotoshopToSpine can be imported into your skeleton, even if the original PSD is different. You can import additional images to your existing skeleton via Import Data… as you did when you created your skeleton first. After unchecking New project, two options appear and you can use the later one Import into an existing skeleton to import additional images. Also, the Ignore option allows you to import only new images to the skeleton.

Therefore, there is no need to hide other layers when exporting them from PSD. (Although hiding them has the advantage of shortening the export time.)

Regarding how to replace images, there are some ways depending on the type of the attachments. If you want to replace the images of mesh attachments, a dialog will appear if the size has changed since before you replaced it. Please see this section of the User Guide for more information:
Mesh attachments - Spine User Guide: Image resize

If your new images have exactly the same size as the old one, you can replace them by using the Replace option of Import Data as described above.

If your new images have different sizes than the old one, but they are region attachments, you can still import them without corrupting. However, the position of the old images will be inherited and the replaced images will be misaligned from the position on your PSD. Therefore, it is better to delete the region attachments you want to replace before importing new images.

I hope this answers your question.

andyhoopper wrote

I have a looped "ear" that I need to rig, but because of the order of the "ear", I decided to split the "ear" into two. I'm having a bit of trouble trying to get them to move together under a nest of bones. Is there a better approach for this?

I'll add my two cents, while as Misaki said, it is quite convenient to keep the images united, you can also very well keep them separate to get a bit of a 3Dish feel to them/have hair pass in between etc.

As your problem is specifically that they don't match, here's how:

• first create one mesh, then activate the wireframe so it stays visible.
• create the second mesh and make sure to place the vertices as close as possible to the other mesh, which should stay visible thanks to wireframe. Pay especially attention that the faint dotted lines that define the triangles are as similar as possible, to get exactly the same deformation.
• when weighting the meshes, make sure that the vertices that overlap are bound to the same bones and the weights you assignto a vertex match the weights you assign to the vertex you overlapped.

Here's a couple of streams where this is also achieved:

oldish stream, but around 1:55:38 you can see how these weights are assigned in the top cape so that it looks as a single piece despite being two separate parts:
https://www.youtube.com/watch?v=dDkIL9Xwm5E&list=PLwGl7Ikd_6GTpd2PnWqqIZVsqotxtrtaE&t=6897s

In this stream various parts of the body are made to look as if the body is a single piece and, you guessed it to not make them look separate, for the vertices that overlap, the exact same weights are used once again:

https://www.youtube.com/watch?v=SroKx9FjNJo&list=PLwGl7Ikd_6GTpd2PnWqqIZVsqotxtrtaE&t=2003s

I hope this helps!