There are a few methods to add blush to doll's cheeks (toys's cheeks). I'll show you the method I usually use in this video.
I usually use my make up blush powder, it's the simple technique. You can use the brush to add the color on the doll’s face.
But the blush doesn’t stay for long, it will fade away when you wash your doll.
So if you want the pink cheeks to stay forever, you can use the acrylic paint. You will add some water with a little pink acrylic paint, then using a brush to apply on the doll’s cheeks.