You can texture the current model with hair stencils, but even with the most photorealistic textures, the final result will just look like a toy with a pseudo-realistic texture on. Imagine putting an perfectly realistic textures on a cube, that would still look like a cube.
Now the most obvious way to make realistic hairs these days is to use hair particles, you would have to spend time combing and cutting the actual hair strands, and then do a nice shader work or import a good hair shader made by someone else. But Blender's Principled Hair shader is already quite nice, you can easily make it better by painting the colors instead of using a unique flat color.
You can also use the hair particles plus some manual editing to make stylized hair particles. You are on control of how much stylized or realistic you want the result, but that method allows you a flexibility in shape that the hair particles alone don´t.
Another method is one used in video games when particles are not possible: hair cards. It can be done either by assigning mesh planes to hair particles, or by modeling the cards manually, or both manually modeling and guiding the strands with nurbs curves.