I am new to Blender. I am trying to learn how to sculpt, but my grab tool only seems to grab a few seemingly preselected vertices. So, when I am trying to create a head and place where the skull connects to the neck or when I try to create a jaw line, the spot or dot that shows where I am grabbing only grabs at a few places and I can not do what I am attempting to do.
As you can see in the pic, I have the grab tool over the shape but no dot. But that dot will show up over some spaces. Why and what am I doing incorrectly?