You can’t tone whenever you want. To achieve the color tone you want, you need your hair to be at the right shade of yellow. If you want a light ashy or cool color, you have to make sure your hair is at a light yellow color before using the toner. If you use toner at the wrong shade of yellow, you won’t get the result you want. Toning works well with bleached hair. To achieve certain shades of blonde, you will have to bleach your hair first and then add toner. Toner also helps even out hair color after bleaching.  Some toners can only be used days after you've bleached your hair. For some desired shades, you have to bleach your hair more than once over a period of time to achieve the color. This is especially true if you start with dark brown or black hair and you’re wanting it to be blonde. Toner can also be used when you dye your hair. Sometimes, the hair color you end up with is not exactly what you want. To help remove certain pigments, like if your hair has too much red or brassiness, you can use toner to even out your dye job or adjust the color. Toner can sometimes be used after a bad or undesirable dye job. It can't change your hair color, but it can even out your shade. Some shades may take time to achieve. This is because your hair may still have too much red or yellow pigment in it to achieve the cool or ashy shade you desire. Listen to your salon professional’s advice to help you work towards eventually achieving the desired shade.  For example, at first you may not be able to get a silver blonde. The silver blonde toner may make your hair green or another shade. Instead, you may have to bleach your hair a few more times before your hair is stripped of the red and yellow. Always keep a color wheel handy while bleaching, dyeing, and toning your hair so that you can pay attention to your hair's current color and undertones. This way, you can avoid ending up with a hair color that’s different than what you were hoping for and expecting.

How would you rephrase that briefly using Vietnamese?
Chờ đến khi tóc có đúng màu để dùng toner. Sử dụng toner sau khi tẩy tóc. Sử dụng toner sau khi nhuộm tóc. Biết rằng ban đầu có thể bạn không đạt được sắc độ mong muốn.