I gave a try to the two mini-projects of Alina Harvi  with oil pastels.

The first one I made with exactly the same Sennelier colors as the instructor. The second I painted with Mungyo oil pastels. Mungyo is fantastic, affordable, but doesn't have really dark colors other than black, while Sennelier has a number of gorgeous dark colors.

I used a white pencil for the drawing of the sketch.

I painted the backgrounds with gouache paints and then I sprayed them with hairspray. It wasn't really necessary, since oil pastels work great on top of gouache.