Blend materials on 2 different meshes

Hello everybody
So I have 3 meshes that have 3 different materials. Places that they touch it looks sharp and I want to put mud or something else 4th material that will blend these or something else that will make smooth transition to eye from material to material, like this it looks unnatural. My thinking was make 3 materials with edge of meshes to be mud so where they meet together there will be mud? But my problem is with nodes how to do that?
tnx in advance