So here's how to make this postcard:
1. Eat all the Alpha-Bits; disassemble the cardboard box
2. Draw the shape of your monster onto the coloured side of the cardboard
3. Cut out and base coat with white gesso
4. Block in colour with gouache (thick highly pigmented paint that covers excellently*)
5. Drybrush lighter colours on to get highlights - you can just add white to your first colour if you don't have two shades
6. Make warty-looking dots by dipping the back of your brush into the paint and dabbing onto the horns
7. Use a Stabilo Marks-All pencil to add outlines and shadows
8. Stand back; admire work; slap a stamp on the back and mail it to someone you like
*yes, I know that's not a word
Go. Make monsters.
P.S. This technique also works with Mini-Wheats.