Which of the following is BEST to consult when in doubt about how to use a product?

Consulting the manufacturer's instructions is the best approach when there is uncertainty about how to use a product. These instructions provide specific information that is tailored to the product in question, including application techniques, safety precautions, and any relevant features or unique properties of the product. Following the guidance provided by the manufacturer ensures that you are utilizing the product as intended, which can help prevent mishaps and ensure safety for both the technician and the client.

While Material Safety Data Sheets (MSDS) are essential for understanding the hazards of a product and proper handling and disposal methods, they may not provide detailed usage instructions like the manufacturer's instructions do. The CDC website offers valuable public health information but is not specifically tailored to individual products. Consulting a colleague can be helpful for personal insights or experiences, but it may not guarantee the most accurate or updated information regarding specific product usage. Therefore, when in doubt, relying on the manufacturer's instructions is the most reliable and effective course of action.