If you use lol maya version 2.3+, you can load skn/skl as a group of meshes, separated by materials (1 mesh = 1 mat)
This allow you to work easier with champ that has multiple materials: you can work with UV that are not overlapped, you can modify this mesh while keeping weights of other meshes without unbind skin.
For example: This is how to swap Qiyana with Garen while keeping her weapon default:
1. Load Qiyana in Maya as group meshes.
2. Unbind Qiyana body mesh.
3. Delete Qiyana mesh, import Garen mesh, make him fit the skeleton (or make the skeleton fit him)
4. Put Garen mesh in the group, assign his body mesh to Qiyana base body material, bind his body mesh with joints. (edited)
5. Paint weight only on him (no need to paint the weapon)
6. Final export: Select the group -> Export selection -> Export as SKN+SKL
You can have 2 meshes that assign same material in the group.
For example: This is how to add Miss Fortune hat to Qiyana without touching her weights and stuffs.
1. Load Qiyana as group meshes + MissFortune hat to scene.
2. You dont need to combine Miss Fortune hat mesh with Qiyana body mesh, you can assign the hat to Qiyana body mat like in the image.
3. Put the hat mesh in group.
4. Now you will see that MF hat UV is overlapped with Qiyana body UV, we need to fix this.
5. Use martin UV helper to quickly fix UV. Yes you can move UV even though the skin is bound, my plugin can still export fine.
6. Now bind the hat mesh with joints.
7. Flood weight the hat to Head influence.
8. Select the group -> Export selection -> Export as SKN+SKL.