I'm getting ready to hand quilt a baby quilt. What is your favorite marker that will wash out?

Dritz water soluable maker pin, blue.

depends on the color of your top. you don't say if it is dark or light colors. how much marking you want to do. hand quilting or machine quilting. type of fabric used.
Lots needs to be known before giving an "informed" answer.

I just posted a picture. I always use 100% cotton.

I usually use a regular pencil and never have a problem. Someone talked me into buying a Sewline fabric pencil (supposedly wipes off with a damp cloth) but I haven't tried it yet.