Prepare the drawing board and gouache paint. It is suggested to choose dark blue, purple, black and white to draw the effect of starry sky.
First draw a dark blue background on the drawing board, which can be lightly daubed with a clean brush or sponge.
Draw the shape of the nebula on the drawing board with white gouache pigment. You can pat or drag it with a clean brush or sponge to let the colors blend naturally.
Draw the shapes of stars and galaxies around the nebula with black gouache pigment, which can be gently drawn with a small brush or cotton swab.
Draw some light around the stars and the Milky Way with white gouache pigment, which can be gently applied with a clean brush or sponge.
Finally, draw some dim colors around the drawing board with dark blue and purple gouache pigments to make the whole picture richer and more three-dimensional.
The above are simple steps to draw gouache in the starry sky, which can be adjusted and improved according to your own preferences and creativity.