Wet-on-wet

Highly translucent and prone to accidents, watercolor paint will bloom in unpredictable ways that, depending on the artist's frame of mind, can be a boon or a burden.

[3] Wet-on-wet painting has been practiced alongside other techniques since the development of oil painting and was used by several of the major Early Netherlandish painters in parts of their pictures, such as Jan van Eyck in the Arnolfini portrait, and Rogier van der Weyden.

Impressionists such as Claude Monet, post-Impressionists such as Vincent van Gogh, realists such as John Singer Sargent and Robert Henri and George Bellows, Expressionists such as Chaïm Soutine and Yitzhak Frenkel, and the Abstract Expressionist Willem de Kooning have in different ways employed this technique, and it is still heavily used by both figurative and non-figurative fine artists.

[5] Artist Bob Ross employed the technique for his show The Joy of Painting in order to produce complete pieces in real-time within a single episode, after learning the technique from his mentor William "Bill" Alexander.

[6] A handful of products exist allowing for the use of wet-on-wet applications in housepainting, but the practice is not widespread.

Frans Hals , Jasper Schade van Westrum (1645); painted mostly wet-on-wet. The forehead has portions of wet (white) over dry (brown/black).
Rembrandt , Portrait of Jan Six (1654) has numerous uses of the wet-on-wet method.
Winslow Homer , Rowing Home (1890), an example of the wet-on-wet technique in watercolor, especially in the sky