Logic issue with clone's materials

Hi all,

Pretty new to Unity, I'm struggling with some logic issues.

I'm trying to create a lighting visualization app. I have a projector made of several meshes that I turned into a prefab. I'm instancing 100 projectors with the following script attached to an Empty Object :

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class projector_instancer : MonoBehaviour {
 
     public GameObject proj_prefab;
     private GameObject proj_array;
 
     // Use this for initialization
     void Start ()
     {
         for (float x = 0; x < 10; x++) 
         {
             for (float y = 0; y < 10; y++) 
             {
                 // Create the clones
                 proj_array = Instantiate (proj_prefab, new Vector3 (x * (float)1.5, y * (float)1.5, 0), Quaternion.Euler(90,0,0));
             }
         }
     }
     
     // Update is called once per frame
     void Update () 
     {
         // Update DP grid size
     }
 }

Now here's the tricky part. I'd like to assign two textures to each clone, each one being displayed on a different "sub mesh" of my prefab. Later, these textures will need to be stretched/offset so each projector displays the part of the texture it's supposed to show (those projectors are actually LED matrices on a moving head).

I lack Unity knowledge and I have no idea where to start :

• Should I create two Material variables on my Instancer script and feed them via Inspector ? Then I would do the offset/scale thingy in the for loop. I understood I have to access the Renderer of each mesh to do so, but I don't understand how to do this, and how to filter those (my prefab actually has more than two meshes).

• Or should I assign those textures to the prefab itself (by drag'n'dropping the mat on the desired "submesh") and then offset/scale the texture in my script ?

This must be simple but my knowledge of how Unity works is pretty limited. Any help greeeeaaaatly appreciated :)

Thanks !