I recommend a scalp hairbrush.

I’ve been finding the Yao Scalp Hairbrush very useful. I use it to massage my scalp while shampooing, and I can actually feel a noticeable difference compared to when I don't, so it has become an essential item for me. The material is flexible, so it feels like it gently rubs the scalp rather than scrubbing it hard; it leaves me feeling incredibly refreshed after a massage. Cleaning is convenient as you can simply put it in water, and the medium size fits comfortably in my hand.