I always do my sketches in acrylic.
This way they can be done quickly and they dry fast, so I can easily turn pages of my sketchbooks during sketching.
One little quick sketch for one little inspirational booklet I`m working on at the moment. some of my sketches end up as oil paintings, some as illustrations for books, some for music projects, some for celtic journeying projects...If I had time to post everything I do I would be posting from morning to evening every day.
( Luckily I live in between so I don`t have a proper perception of flow of time XD )