How to cut your assets for animation
Give Erika a piece of advice.
The hyphen (-) is not safe in a development environment. The underscore (_) is a safe character, so it is generally used instead. :
Which part that uses hyphen would affect code?
Personally I greatly dislike underscore. It's too large and makes things ugly, particularly with variable width fonts, but I also don't use it in code with fixed width fonts. In Spine projects I use hyphen and encourage it. All our examples use hyphen. The names of things in your Spine project don't appear in code verbatim and camel case is better IMO. 
Space is also OK in Spine projects and I would prefer space to underscore, even with the drawback that you can't see it.
It's not better though. Which character to use in your naming is purely subjective. Use whatever looks good to you: hyphen, space, underscore, or anything else. The choice has no affect on code. What other large projects use doesn't matter.
Yes, so it's just a suggestion. Because I like watching Erika's videos. But then I saw some actual job requirements and felt a bit disconnected. Don't worry about this issue. - More aesthetically and linguistically.
Thank you so much Erika for the huge effort in making this guide!
This was sooo needed!
I'll have to remember that this exists now, whenever I need to explain this topic to somebody new 
Are you considering a Part 2 with more specific cases?
Like how to divide a light or a shadow from the object it's cast upon, with possible Colour Blend modes, or how to behave with particles where you can use one signle image and repeat it in Spine?
Ah that's a neat idea! Let's gather some ideas/topics/requests that are more specific here! when there are enough I'll detail them in a new article and link back to it in this one so it's easy to find 
- divide light and shadow for animation
- how to consider blend modes when preparing assets for animation
- what to do with particles or objects that repeat a lot
- how to prepare hair for animation
if we can find 2-3 more that would be already enough for a second blog post!
Cutting assets is very goal oriented -- it entirely depends on how you need your skeleton to move. Inevitably you didn't plan for some movement and now need to adjust the existing rig, probably with existing animations.
PSD tags are pretty closely related to cutting up assets. That's a big topic to cover though. 
Still it might make sense to cover basics, or actually skip the boring basics and cover the top 1-2 most useful PSD techniques people are likely to need after the basics.