His technique relied on precise lines and a muted palette. Mestler often utilised watercolour to capture the specific quality of light in New England. In works like Boston Skyline Along Charles River, he avoided romanticised views of the city. He preferred to focus on the stark relationship between water and stone. His botanical studies, such as Männertreu, show a similar discipline. He treated the Alpine orchid with the same analytical rigour he applied to brick and mortar. This precision distinguishes his work from more expressive movements of the mid-twentieth century.

Modern collectors value Mestler for his ability to convey a sense of stillness. His series The Loneliness of an American Winter resonates with those who appreciate minimalist compositions and quiet moods. These prints provide a calm aesthetic for contemporary interiors. The work functions as a study in form and space. It offers a restrained alternative to more decorative styles of art. His ability to find order in both nature and the city makes these pieces versatile for home display.