If clumps still form despite taking preventive measures, there are a few steps you can take:   Stop mixing and let the mixture sit for a short while. This can allow the plaster particles to absorb water and soften, making it easier to break down the clumps. Use a clean tool or mixing paddle to break up the clumps by gently pressing against them and stirring the mixture. If the clumps are stubborn, you may need to discard the clumped portion and prepare a new batch following the proper mixing techniques.   Remember, practice and experience can also play a role in achieving a smooth plaster mix. With time, you will become more adept at identifying the correct consistency and achieving a clump-free mixture.