Discovering these kits has been a revelation to me. They are so well produced, and add such subtlety and nuance to an artwork, that they pay for themselves straight away. Here you get more texture brushes than most people could use in a lifetime, and since they can be mixed in any combination, the creative possibilities are pretty much infinite. If you've never bought an add-on kit, this is well worth trying out. The documentation, support and community is second to none.