Here are the links for Buttery Oils. One will install a category to the library of your choice and the other will install a Buttery Oils Library.
My recommendation is to put the Buttery Oils Category in the Bristly Dab Library. Buttery Oils and Bristly Dabs work very well together. Putting Buttery Oils inside of the Bristly Dab library will allow you to switch between the two categories easily.
This is Buttery Oils Category
This is buttery Oils Library
Please let me know if you have any trouble downloading or installing brushes.