Banana yellow, flat-ironed ends, toffee-blond frizz and brunette layers — Hilary Duff‘s hair evolution has spanned all colors, textures and lengths since the Disney star turned pop singer erupted onto the scene in the early 2000s. Now she’s onto something new.

In a recent “Call Her Daddy” interview with host Alex Cooper, the 38-year-old artist donned loose, honey-blond waves. The effortless aesthetic, dubbed “cool girl waves,” was the work of her longtime hairstylist Barb Thompson, whose A-list client roster includes Emma Stone, Keri Russell and Sarah Paulson.

“Creating that signature bounce on Hilary Duff for ‘Call Her Daddy’ was all about building airy structure from the prep stage. Lightweight hydration, strategic blow-dry memory and then sealing it with soft movement rather than tight curls,” Thompson told WWD in an exclusive statement.

To prep the actress’ hair, Thompson used Surface Hair’s All in One Leave In Conditioner. Formulated with amaranth protein, cocoa butter, hemp seed oil, moringa oil, rice protein and babassu oil, the product doubles as a detangler and a heat protectant.

Next, Thompson coated Duff’s hair with the Blowout Primer. “I followed with a 2.5-inch round brush to sculpt a smooth, airy base that still has movement. A blow-dry like this is also an important way to create the perfect canvas for curling iron work,” she said.

For a sleek, frizz-free finish, Thompson spritzed a bit of the Surface Hair Blowout Finishing Spray before going in with a 1.25-inch curling iron, which she used “through the back and worked up the head.” The top sections were then curled with a 1.5-inch barrel. The key, Thompson said in the official press release, is to curl small sections away from the face, let each section cool and flip the hair a few times once it’s finished.

“I focus on keeping the finish touchable and modern so the volume feels effortless, never overdone. The goal is a polished blowout that still has that cool, lived-in energy when she moves,” Thompson told WWD, adding that a texture spray and dry shampoo foam can help add volume and lift the roots.

The poster girl for Y2K beauty, Duff is best known for her blunt, blond bangs as Lizzy Maguire and Samantha in “A Cinderalla Story.” But there were two years, 2005 to 2007, when she went full-blown brunette, starting with a subtle caramel-copper blend and ending with a dark bistro shade. During this time, she would often style her hair in a side ponytail, with small sections left out to frame her face.