All perfect praise be to Allah. May all his blessings and peace be upon Prophet Mohammad and upon his family and companions.
In principle, all parts of the swine are impure: its flesh, its hair, and its skin…etc. This is because Allah Says in this regard: “Say: "I find not in the message received by me by inspiration any (meat) forbidden to be eaten by one who wishes to eat it, unless it be dead meat, or blood poured forth, or the flesh of swine,- for it is an abomination - or, what is impious, (meat) on which a name has been invoked, other than God’s". But (even so), if a person is forced by necessity, without wilful disobedience, nor transgressing due limits,- thy Lord is Oft-forgiving, Most Merciful.” {Al-An`nam/145}.
Muslim jurists agreed that selling any part of swine isn`t permissible save in case of necessity, so using a shoe brush made of swine hair isn`t considered a necessity as it can be replaced with one that is made from pure ingredients whether they are synthetic, or natural. On the authority of Jabir Bin Abdullah, Prophet Mohammad (PBUH) said: “Allah and His Apostle made illegal the trade of alcohol, dead animals, pigs and idols.” {Bukhari&Muslim}."
It is stated: “The issue of making the use of a dog`s and a pig`s skin and hair illegal when there is no necessity for using them is parallel to the use of what is called ‘Chitah” because it is made from swine hair. Yes, if using flax was dependent on using the “Chitah” and there was no other alternative, then it is a necessity that permits using it, and the impurity resulting from touching the item in case it was wet is pardoned." [Hawashi Asharwani wa Alabadi, v3ol./pp.31]. And Allah Knows Best.