Jackson's Art - The smoothest shading results can be most easily achieved by using Zest-it Pencil Blend. It is a solvent that will break down the oil and wax content of pencils,
Zest It Pencil Blend Hack! // TUESDAY TIP - YouTube
24 WAYS to Blend Colored Pencils – The Ultimate Blending Comparison | Blending colored pencils, Coloring tutorial, Colored pencils
Zest It : Pencil Blend (Citrus Free) | Jackson's Art Supplies
Zest-it Pencil Blend 125ml - The Deckle Edge
Zest-it 50 ml bottle pencil blending solution | PaperStory - The Great Little Art Shop