For Inuyasha's ears, I recommend felt over fabrics. Rather than just sewing two triangle peices together for the ears, if you use felt, you can more effectively get the right look and shape of Inuyasha's ears.
For my Inuyasha costume, I used felt for the ears. The white actually folds over the pink felt for the more authentic Inuyasha ears. It's quick and very easy. From there, it's just a matter of handsewing the ears to the wig. That is, as long as you don't plan on using the wig for other costumes.