Android scratch View 2 Layers - imageview

Question

I'm using Android-WScratchView to implement a scratch effect in my app.
What my app does is a "cleaning" effect. I have a picture of a clean t-shirt and another picture of the same t-shirt but dirty (with some mud).
Android-WScratchView works great for the normal case, a background Image (clean t-shirt) and an overlay Image (dirty t-shirt).
The problem is now, I need to add a second overlay Image, which is a "less" dirty t-shirt so the user has to "clean" the t-shirt in 2 steps.
Once the first layer has been erased, I need to be able to erase the second layer but only where it is visible.
I've implemented it using 2 WScratchView objects, one behind another, like this:
<ImageView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#drawable/shirt_clean" />
<com.winsontan520.WScratchView
xmlns:wsv="http://schemas.android.com/apk/res-auto"
android:id="#+id/scratch_view_layer_1"
android:layout_width="300dp"
android:layout_height="300dp"
wsv:antiAlias="true"
wsv:revealSize="20dp"
wsv:scratchDrawable="#drawable/shirt_less_dirty"
wsv:scratchable="true" />
<com.winsontan520.WScratchView
xmlns:wsv="http://schemas.android.com/apk/res-auto"
android:id="#+id/scratch_view_layer_2"
android:layout_width="300dp"
android:layout_height="300dp"
wsv:antiAlias="true"
wsv:revealSize="20dp"
wsv:scratchDrawable="#drawable/shirt_dirty"
wsv:scratchable="true" />
The problem is that after the "most dirty" layer is "erased" (it gets transparent) I cannot delete the "less dirty" layer because the second layer is getting the onTouch event.
My idea is parsing somehow the onTouch event through the second WScratchView to the first one. But still would have the problem that I don't know which area has already been deleted and which not.
I would appreciate any help, also a different way to implement it will be accepted.