Waterfall Material's Vertex Color Method
This video covers the basics of using Vertex Colors in a material to change which textures/nodes show up on parts of a Mesh (that has Vertex Colors painted).
You must actually make distinct vertex colors on your mesh or none of this will work. You can change your mesh Vertex Colors either in your 3d package such as 3DS Max or Maya OR you can paint the vertex colors IN Unreal 4 then save your changes. I'm not going over those details in this video. Painting vertex colors on meshes is not very difficult or complicated and there's no one "right" way to go about it, pick the way that works for you.
SORRY I KEEP SIGHING - I WILL NOT LET IT HAPPEN IN FUTURE VIDEOS, YES I KNOW IT IS ANNOYING, MY BAD!!!