Francis Danby (1793 — 1861) The Procession of Cristna Watercolor and gouache, heightened with white gouache, with gum arabic, some scratching out, on vellum The Pierpont Morgan Library, purchased on the Sunny Crawford von Bülow Fund, 2001.18. (themorgan.org)
For the white stars and lights on the tree, I used white gouache paint. (jonesdesigncompany.com)
Instead of using white gouache or Chinese White, you'll need to plan a bit more beforehand to reserve the white areas and possibly use masking fluid for the mast, the boat and maybe the roof of the building and the waterlines around the banks. (arttutor.com)