One of my favourite sketching tools is a Tombow dual brush pen – fine tip one end for consistent lines, and a brush tip on the other which works like a paintbrush to create fine, medium or bold strokes. They come in a wide range of colours but I find just a few shades of grey useful for quick sketches. I like to use a light grey fine tip for initially outlining the basic shapes, then switch to the brush end for blocking in and for shadows.
The following sketch was done while filling in 15 minutes waiting for my taxi. The brush end allows me to fill in larger areas quickly. I added the colour on the sculpture later as my ride appeared too soon.
Another journal sketch of a little cottage opposite a local park on Strathmore toned grey paper, was done the same way, adding ink linework over the initial Tombow sketch, then colour with watercolour pencils used dry. The grey paper works well, providing a mid tone background, with the Tombow for shading, black ink linework and a white Posca pen for highlights.
The next sketch was done the same way, sketch with the light grey Tombow, adding the shadow areas before adding Ink and colour with Portfolio water soluble oil pastels, a set I picked up some time ago but rarely used. I believe these are childrens crayons, but similar to Neopastels. Probably not archival but fun to use for sketchbooks.
Like many artists I find it hard to resist new art products, which seem to keep on appearing on each visit to the art supplies shop. But I am sticking fairly well to my resolution early this year not to buy any new products (apart from replacements), and to use up what I already have.