I always use one on my pillow. I use it so that I don't rough up my hair when I sleep. I am growing my hair out and the slipperiness is kinder than my cotton pillowcases. So, in that respect, I guess it does prevent some frizz.

I just bought a set of 2 that were billed as "premium". They tend to absorb the oils from my hair and face so having 2 allows me to change them frequently.
3b spirals, fine texture, normal porosity, dense
Deva Low Poo
Suave Naturals Coconut for detangling
Renpure Organics conditioner/leave-in
Homemade FSG
Curl Junkie Stuff

Nothing lasts, nothing is finished, and nothing is perfect.