I've been speaking quite a lot recently at Photography and Camera Clubs, and one of the things I am asked all the time is to demonstrate an easy way to do Frequency Separation in Photoshop. So I have put together an easy guide Youtube tutorial on how to do this. This is an easy to follow demonstration of the process and formula required to separate your colours and textures out. As like anything thing in Photoshop, there are many ways to do a Frequency Separation, but this is just one of the easier ways I know which may help you if you wish to give it a go!
Happy Editing!
Vx