The particular brush has its own name, the shoebrush or shoe-brush, but dictionaries cannot agree, even with themselves, on which form is proper. It would be prudent to just use the two word form.
(our spell-checker doesn't like either one)
Before 'running shoes' were so popular, shoes were mostly made of leather. They needed to be cleaned with shoe brushes, often 3 of them, one to brush off mud etc, one to apply polish and one to shine the polish. A dying tradition, but I, for one, refuse to wear 'running shoes' for regular attire.
It is one word.
Its one word
One, it's a compound word.
It is one word.
one word
Schoolchildren, one word.
It is one word
One word. 'Sandstorm.'
It is one word.
one word
It is one word.