Do I need to download anything else to get grease pencil working in blender 2.8 build? I literally just unzip the zip file and grease pencil doesn't show any strokes when I draw. I watched some grease 2.0 previews and I'm very interested but it doesn't work for me right now. All settings are on default and I reset settings many times also downloaded both x64 versions to try, same result. My brush color is black nothing shows up on white background. What am I doing wrong? 

Edited: Just to clarify somethings here, I'm currently using 2.8 not 2.78 build. I know you have to press D then draw, but it currently doesn't work in the 2.8 version that I've downloaded. My 2.78 grease pencil works just fine.
2.8 Grease Pencil Branch is not the same as the builder.blender.org 2.8 branch builds, as you need to compile the separate gpencil branch yourself.