A process for the multilayer coating of substrates comprising the steps: 1. Applying a filler layer of a filler coating composition onto an optionally pre-coated substrate, 2. Applying a base coat layer of a water-based base coat coating composition containing color-imparting and/or special effect-imparting pigments, one or more binders, water and optionally at least one of the following constituents: crosslinking agents, fillers, conventional coating additives and organic solvents onto the filler layer, 3. Applying a clear coat layer of a transparent clear coat coating composition onto the base coat layer and 4. Curing the clear coat layer, wherein the filler coating composition being an organic solvent-based coating composition comprising: A) at least one binder with functional groups containing active hydrogen, B) at least one polyisocyanate cross-linking agent with free isocyanate groups and C) at least one epoxy-functional silane of the general Formula: X denoting the residues with m being 1-4, or epoxy cyclohexyl, R1, R2, R3 mutually independently meaning identical or different organic residues with 1 to 30 carbon atoms per molecule, providing that at least one of the residues is an alkoxy group with 1 to 4 carbon atoms and n is 2, 3 or 4. 1. Applying a filler layer of a filler coating composition onto an optionally pre-coated substrate, 2. Applying a base coat layer of a water-based base coat coating composition containing color-imparting and/or special effect-imparting pigments, one or more binders, water and optionally at least one of the following constituents: crosslinking agents, fillers, conventional coating additives and organic solvents onto the filler layer, 3. Applying a clear coat layer of a transparent clear coat coating composition onto the base coat layer and 4. Curing the clear coat layer, wherein the filler coating composition being an organic solvent-based coating composition comprising: A) at least one binder with functional groups containing active hydrogen, B) at least one polyisocyanate cross-linking agent with free isocyanate groups and C) at least one epoxy-functional silane of the general Formula: X denoting the residues with m being 1-4, or epoxy cyclohexyl, R1, R2, R3 mutually independently meaning identical or different organic residues with 1 to 30 carbon atoms per molecule, providing that at least one of the residues is an alkoxy group with 1 to 4 carbon atoms and n is 2, 3 or 4. A) at least one binder with functional groups containing active hydrogen, B) at least one polyisocyanate cross-linking agent with free isocyanate groups and C) at least one epoxy-functional silane of the general Formula: X denoting the residues with m being 1-4, or epoxy cyclohexyl, R1, R2, R3 mutually independently meaning identical or different organic residues with 1 to 30 carbon atoms per molecule, providing that at least one of the residues is an alkoxy group with 1 to 4 carbon atoms and n is 2, 3 or 4. X denoting the residues with m being 1-4, or epoxy cyclohexyl, R1, R2, R3 mutually independently meaning identical or different organic residues with 1 to 30 carbon atoms per molecule, providing that at least one of the residues is an alkoxy group with 1 to 4 carbon atoms and n is 2, 3 or 4.