Really Struggling With Adding Dirt

[agentorange]

Need some help with this. I have a leather material with Bump, Gloss etc etc added and I need/want to add a 'dirt' to the objects.

I have produced to different materials and have tried to create a multi material with using both.....not working and finding it hard for finding a 'Slot' of where to put my dirt without destroying the original red leather material.

I know this is gonna be a simple solution - but can't see the wood for the trees...

Vray 3.4 b2 on Sketchup Pro 2017

Cheers,
Drew

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[agentorange]

Well after a day full of trial and effort I finally got there....