I had gotten several packs of brushes for essentials and I was really loving them. I was assuming I'd still be able to use them once I upgraded. However it doesn't seem to be working. Is this not something I'm able to do? I really loved the hair brushes and lightning brush packs.
I believe they are incompatible. Your best bet may be to approach Support. I was able to replace my "Magic Mountain" brush set in Essentials 6 with the equivalent Painter version after asking Support nicely (although it was only provided as a download and not as a "purchase", so I have to be careful to back it up).