Assistance with Brain MR segmentation?

Hello! I am new to the slicer community. I have tried multiple attempts at segmenting out my brain, however continually fail to achieve the quality I am hoping for. I have watched multiple videos to no avail. The sulci/gyri are very pixelated rather than smooth. Goal is to 3D print it. Any advice and help would be greatly appreciated! Would be happy to share the file for reference if that would be helpful!

Thanks!

I always suggest SuperSynth: SuperSynth - Free Surfer Wiki