How do I use the paint brush with a fill in illustrator?

Question

I'm watching the video at https://www.youtube.com/watch?v=cljS0rL5-Ko . The video's author uses the paint brush tool with a fill and a stroke to draw the character.

Every time I try to draw with a brush that contains a fill, the fill gets removed as soon as I start painting and only the stroke is left.

Why does the fill get removed and how do I include the fill while drawing?

I'm using Adobe Illustrator CC on a mac.

Answer 1

Double-click the Brush Tool and tick the "fill" option.