His book, Biographical and Critical Dictionary of Painters and Engravers, first published in 1813–1816, was a standard reference work (revised, and often under variant titles) throughout the 19th century, and was last republished in 1920; however it is now badly outdated.
He travelled to London in 1781, then to Flanders with his eldest brother, where he lived from 1782 to 1790, possibly having some connection with the cloth trade, but also building up his art historical knowledge.
It was here that he met François Laborde de Méreville who, in 1798, sought his advice and assistance in disposing of the Italian part of the famous private "Orleans Collection" of art which he had acquired.
After three weeks, a syndicate consisting of the Duke of Bridgewater, Marquis of Stafford, then Lord Gower, and the Earl of Carlisle, became the purchasers of the collection from Bryan, at a price of £43,500.
[3][6] In 1801 Bryan obtained, through the Duke of Bridgewater, the king's permission to visit Paris in order to purchase art from the cabinet of Monsieur Robit to bring back to England.