Slate Brush Using Custom UI Material Z-Order Issue

I have overlapping slate brushes, which if drawn sequentially using a texture as the resource object, obey the draw order in regards to z-order - that is, brushes drawn last appear on top.

If I change the resource object to a custom UI material, this no longer happens. Draw order seems randomised.

Looking for some help on how to address this in custom UI materials?

The material in question is just a UI material set to Translucent blend mode, with a texture’s RGB piped to Final Color, and A piped to Opacity.

EDIT: Solved it I think. Just need to increment the layer id.

EDIT: Nope, that makes the brushes draw over the Unreal interface.