Layered material?

Hallo this is my first post so bare with me please if i screw up on some rules. I’ve been working on a little free time project after school which i’ve been working on for 4 months now. and so far it’s been awesome to learn about all the stuff that goes into making game assets and so on. but I’ve kinda run into a bump lately.

so im making a city im calling Rønjeborg. and the way i will go about it. was kinda like skyrim’s whiterun. where its a model the terrain. but here came my problems i have no idea how to break up the uv’s to blend the matierals correctly. and would much rather have a method more like terrain painting where i can paint the diffrent matierals on. actually idk what i really want i just have no idea how to go about making this. so if you know anything or have seen any tutorials on something that sounds like it would be helpful to me, bring it! and i will be forever grateful.
Here are some Pictures of the work-in-progress city
This is the material i want to Blend

This is the platform

This is the city layout so far

This are some pictures of the area in front of the town. this i made in UDK3. and still speculating over how to import to Unreal engine 4

best regards OMGconex

i tryed making a 3 way blend materiel. but it seems i dont have enough resolution to make any detailed transitions. and would i be able to a transition based on a mask texture ? or something more detailed then just a round brush

you’ll probably want more polygons for a more controlled transition. as far as using a texture to make the blending nicer -