Comerford acquired his early artistic skills by copying paintings in Kilkenny Castle, Carrick-on-Suir and other towns in the south-east, and he for some years he worked as portrait painter in oils in Kilkenny, Waterford, Carrick-on-Suir, other nearby places.
Among his earliest works are portraits of Dr Edward Walsh (see No 116 below) of Carrick-on-Suir and his family. From Kilkenny, Comerford moved to Dublin, although we do not know when exactly.
From then on, Comerford generally worked in watercolour on ivory, using loose brushstrokes.
His miniatures are relatively and are well-drawn, and the features of his sitters are relatively large and well-drawn.
Although by then he was established as a miniaturist, John Comerford remained unknown to the Dublin public as an artist until 1800. Meanwhile, his style was influenced by a meeting in 1799 with the English artist George Chinnery (1774-1852), who was practising in Dublin from 1795 to 1802, and who had married in 1799.