Naomi Watts in straight, beachy and updo hairstyles. Photos: Ray Tamarra/Getty Images | Dimitrios Kambouris/Getty Images for Veuve Clicquot Polo Classic | Theo Wargo/WireImage

Naomi Watts is going to great lengths for Pantene.

The 42-year-old British-Australian actress has been very outspoken about her fine blond strands since joining the hair care brand as its latest celebrity spokesmodel. "I want to let women with fine hair know that achieving beautiful, voluminous hair is possible without damaging your hair or adding extensions," said Watts.

To prove the effectiveness of the Flat to Volume Collection, she even went natural in the line's accompanying ads -- skipping extensions, texture-altering chemicals or other hair tricks.

Now Watts is lending her voice to Pantene's Beautiful Lengths program -- a campaign that encourages women and men to donate their hair to make real wigs for those that have lost their hair due to cancer treatments.

StyleList attended a launch party in New York City where we previewed a short documentary on the charitable initiative and talked about all things hair with Watts.

On her hair routine...
I love that I can be versatile with my hair even though it's fine. I can get body if I want it, go curly or dead straight. I like to change it. I'm not one of those women that wants the same hair everyday and I like changing the length as well.

I'm not very good at doing my own hair. I'm a roll-out-of-bed person, then shampoo and conditioner. At the most, I'll just scrunch it and get a sort of je nais se quoi beach look, and for this length that's the best thing. This is the longest I've had it for a while, so it's a bit more consistent because when I had the bob, one side could be curly and the other straight.

On Pantene...
Tried-and-true products that have always been around. When I travel, I'm not one of those girls that takes their hair dryer and shampoo... I just don't do it. I'll use whatever is in the hotel, but when I go to weird countries, it's the brand that you recognize. So, I was quite genuinely thrilled when they asked me [to be a spokesmodel] because I'm not someone with great hair.

On her favorite products...
The Flat-to-Volume collection is designed for women with my hair type, so I like the shampoo and conditioner, the Triple Action Volume Mousse and heat protectant, which is great for my work when people are coming at you with hot irons all the time. It gives you shine!

On taking care of her hair...
It looks nice thanks to his [Pantene celebrity stylist Danilo] expert hands. It's a process. I work on it and am more conscious about treating it well. When you're an ambassador for a hair brand, it's best. I like as minimum maintenance as possible. I don't want to use a million products so I expect a lot out of my shampoo and conditioner.

On how she manages her strands during sweltering summer days...
The hair changes throughout the day. I can start off scrunching and tousled and then if it's too hot, it just ends up in a ponytail.

Click here to discover the one beauty product Naomi Watts can't live without.