Accepting Bawor senpai request, I made simple masking tutorial. Actually I confused what should I write since I seldom using masking. And the only purpose of masking that I often use is selection. So I will give selection tutorial with masking at Adobe Photoshop. And since he also ask to selection nested hair, I pick this image.

CLICK IMAGE TO GET REAL SIZE

1. Open the image and click on MASKING TOOL. After that, using BRUSH TOOL (B) to brush to make selection.

2. Tips : Use Zoom(Z) to make view bigger and it detail easier to be processed. Press ] to make the brush bigger and use [ to make the brush smaller. Use smaller brush for small part of hair. Space to make our canvas moving to direction and make it easier to control

3. This is my nasty result. I only need less than 10 minutes. If U have tablet, it will be looks smoother. I only using mouse

4. Bring it back into normal mode (Left button of masking button ). Dont forget to Select Inverse the selection by pressing Ctrl+Sift+I

5. I prefer make new layer to re color her hair. So I press Ctrl+J to copy the selecting area into new layer

6. Use Ctrl+U to control the color, Dont forget to click Colorize. I pick this green because I bought Shasha hair color spray light green. lol For my own private photo collection

7. Change the Layer mode into Color

8. And with a little modification, I got this ^^

if U have any question, pls feel free to ask me again ^^