Must be having one of those old-style toothbrushes with the thick and few bristles, all in a row.
I just remember that "fog" means tooth. I picture a fog coming out of someone's mouth, like really bad breath!
Often in English, for example when we correct a learning child, we say 'This is not a toothbrush, it's a comb!'.
'This is not a toothbrush, but a comb' sounds somewhat archaic. Although I understand the distinction in Hungarian, I wouldn't translate this literally.