His technique relied on the traditional method of line engraving on copper and steel. He translated the oil paintings of masters like Sir Joshua Reynolds and Sir Thomas Lawrence into monochrome prints. Works such as Lord Heathfield and Shylock and Jessica demonstrate his ability to translate textures and light using only varied line weights. He avoided the softer effects of mezzotint, preferring the clarity and sharp definition that line engraving provided for historical and literary subjects.

Modern collectors value Doo for the graphic clarity of his compositions. His prints of Shakespearean scenes, such as Bassanio and Portia, offer a structured aesthetic that fits well in contemporary interiors. These works provide a link to nineteenth-century academic art without the heaviness of dark oil pigments. The clean lines of his engravings make them suitable for minimalist framing in a study or hallway.