His parents were descendants of Scottish settlers who lived in Dunedin, and they bought their own farm of 400 acres (1.6 km2) at Mataura Island, Southland.

The four directors who met him off the train, astounded at his youth, advised him of the difficulties of managing a dairy factory on the West Coast, and offered him the chance to withdraw.

While at Totara Flat, Brash was rebuked by the local Presbyterian minister David Anderson for his lack of faith, and his indulgence in drinking, swearing and gambling.

As a result, he became a regular attendee and committed member of the Presbyterian Church of Aotearoa New Zealand.

[2] In 1910 Brash and his family moved to Wellington where he joined the National Dairy Association of New Zealand as an assistant secretary.

Other business ventures included Brash's role as director and chairman of a salt-producing company at Lake Grassmere.

In the 1951 New Year Honours, Brash was appointed a Commander of the Order of the British Empire for services to the dairy and fruitgrowing industries.

Brash was a keen supporter of the ecumenical movement, laying the foundations for the more prominent role of his son Alan.