The Neopets site itself does not offer a tool that allows you to generate random paint brush combinations. The only way to get paint brushes is through:
* Buying them: You can buy them in the Neopets Shop using Neopoints.
* Trading: You can trade for them with other Neopets users.
* Winning them: You might win them through games, events, or contests on Neopets.
Be careful of websites claiming to offer paint brush generators. These are often scams designed to steal your Neopets account information. The only safe place to get paint brushes is through the official Neopets site.