I stated with a rough pencil sketch then inked it with a brush pen and colored it with watercolor and gouache on a watercolor postcard. Reference I used was this excellent photo - https://www.pexels.com/photo/tree-wild-squirrel-monkey-97827/ photo by Mike from Pexels.com
Watercolour pencils and gouache on A4. I did this today at a Urban Sketchers meet up in the National Museum of Scotland - although, I guess, strictly speaking it does not fulfil the urban sketching requirements :D
This is an old Formula 3 race car built by Joseph Potts ltd, Lanarkshire, in 1952. They have it in the National Museum of Scotland, where I drew this a couple of weeks ago as a part of Urban Sketchers meetup (as it’s too cold to go outside yet). This is pretty mixed media: pencil, watercolour pencil, white gouache and some acrylic markers. Drawn on spot.