[skwasjer]

My post was just a short version of the walkthrough I posted. There I explain how you add the modifiers.

This is the excerpt, notice the bold part:

1. To add extra UV-data to the model do the following steps, for EACH next map channel:
2. Select the imported model
3. Click the menu Modifiers > UV Coordinates > Unwrap UVW. A new 'Unwrap UVW' modifier is added to the modifier stack.
4. In the parameters of the new modifier, change the map channel to the index you are about to add. If you have previously exported -uv2, set map channel 2, etc.
   
   
5. After changing the map channel, you will be asked:
   
   
   
   Click 'Yes'
6. Now click the 'Load' button, just above the field where you changed the map channel. You can now select the .UVW file that you want to load into this map channel.