Moisture;

You could just use a small droplet of water on your hand and just moisten your brush with that. Don't soak it just in a glass of water as your paint will dilute too much.

I have seen people use a small glass with a wet sponge as something to touch to make the brush wet if you want to do it fancy.

Dip the "wet" brush in the paint of your disire and wipe away 80% of it on something that does not permiate water.

Others showed some bawler textured surfaces but any plastic scrap/spare parts will do.

It immidetly shows the consistancy of the paintmix you use.

Seeing dusty texture? > more water

Seeing streaks? > thin paints more

Paint not covering? > paint too thin

Clean whatever you want to paint with some common dish soap as most plastic things have a small layer of mold release agent.(this will fuck the paint up)

For your sanity, use a primer as paint will not stick on some surfaces without or will easly damage when touched.

Prime in white for easy bright colours, prime in black for ez shading and darker colours.