How can I check for flipped normals in my avatar and fix them?

In Blender, you can use the 'Face Orientation' overlay (under 'Overlays' in the viewport shading options) to visualize normals. Blue indicates correct orientation, red indicates flipped normals. To fix them, select the problematic faces and use 'Mesh > Normals > Flip' or 'Mesh > Normals > Recalculate Outside'.