How would you introduce a riseball to a young pitcher? Darkened seams might be easier for you to see, because you have years of practice, but I guarantee they look very different to an 11 year old who is just understanding spin.
I use the darkened seams to teach spin awareness. One they recognize spin axis, they can learn the adjustments needed to create backspin (or drop spin.) They pick it up pretty quickly. I teach the catchers as well so they can help their pitcher.
FanFav, do you do lessons/camps up in WI?
Not sure if this product was licensed through Bownet, but I had bought one a few months ago from them. I use it periodically in lessons, and find it effective when emphasizing proper spin direction for fastballs for younger kids. I have not experimented with other pitches as of yet