These are the materials I used. I mixed between Prismacolor and Faber Castel Polychromo pencil sets. Both of these pencil sets are really enjoyable to use with vibrant colours and they blend so well. Only downside to the Prismacolors is the inner crayon cracks quite a lot. These Pencils are extremely time consuming as well since there is a lot of layering but it does create quite a smooth and fluid effect. I also used some gel white pens to use for white highlights in certain areas.
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Callum Warren 
awesome!