Mullins, a landscape painter, was trained by James Mannin in the Dublin Society's Drawing School beginning in 1756.
He was first employed in Waterford where he painted trays and lids for snuff boxes.
[1] He was hired by Lord Charlemont to paint decorative pictures for his Marino estate.
Mullins was also employed as a sign painter and taught one of the premier future Irish landscape painters, Thomas Roberts.
[2] He married a young woman who kept an alehouse near Temple Bar, called the Horseshoe and Magpye, a place of popular resort.