I often use beads, but only on art quilts. If your pillow top is one that is going to be leaned on or sat against, would they be an irritant? If not, I use Silamide, a waxed bead thread and I double it because of sharp edges a bead may have that could rub against the thread and wear through it. I use a size 10 John James appliqué needle -- thin and medium length. Usually I go through a bead twice with it, making sure the holes in the beads aren't pointing upward and don't show. It's lots of fun and the hardest part for me is knowing when to stop so I don't over-do. There are probably videos on YouTube that would be helpful.
I used to put beads on wearable art and loved the process. It leads to a good bead collection and more fun.