Although the exact diagnosis of that white layer can be established after a proper clinical evaluation or at least a look at the clinical picture of the affected area, they are some simple conservative suggestions that can be given to you. Do not use a tongue cleaner whether plastic or metallic or wooden to clean your tongue and only a toothbrush should be used for this purpose. Make sure you clean your tongue after every time you brush your teeth. Maintaining adequate level of hydration is equally important. You can please post a clinical picture if possible for a more streamlined opinion. Regards