How To Use Shampoo Bar Correctly. If your hair is very thick or long, you can double the amount you use, but you shouldn't use a full handful of shampoo on your head no matter how long or thick your hair is. When you’re in the shower, lather your scalp and hair with the shampoo bar either by rubbing wet hands over the soap and then over your scalp and hair, or rubbing your scalp with the shampoo bar.
Apply the bar to your wet hair. Whether you are an amateur or a professional, using a clay bar is something that you are going to come up against if you are chasing that perfect finish. The purpose of shampoo (liquid or bar) is to clean your scalp and remove any oils.
Regardless of the formula of your shampoo, you should focus its use right at the scalp.
Grab a small amount of clay and knead it into a flat, oval shape. For this, you can use clay lubricant, plain water, or a mixture of water and car shampoo. Use it how you would a shampoo: You will probably find that after using a shampoo bar and rinse that you no longer need to use conditioner.