JONATHAN ProductRoot Touch Up, Brunette, Cover Up Your Gray Hair Between Coloring

What happens if you sweat or if it rains?

do you know how many oz this bottle holds?

What's with the stick in the middle of the brush? When I saw it online before purchasing I assumed it served some purpose but I can't tell what now.

I am a black woman with thinning edges. Tried everything. Has anyone used this product to camouflage thinning edges?