How to add layered navigation on brand page - Magento 2

Question

I have used extension(Solwin_Ourbrand) for Shop by brand page.

http://inheritxdev.net/solen_magento/brands.html

On brand page I need layered navigation of that custom product collection.

See brand page : http://inheritxdev.net/solen_magento/brand/accuton.html

I had tried by changing the xml file of that extension by adding the below code.

<referenceContainer name="sidebar.main">
        <block class="Magento\LayeredNavigation\Block\Navigation\Category" name="catalog.leftnav" before="-" template="layer/view.phtml">
            <block class="Magento\LayeredNavigation\Block\Navigation\State" name="catalog.navigation.state" as="state" />
            <block class="Magento\LayeredNavigation\Block\Navigation\FilterRenderer" name="catalog.navigation.renderer" as="renderer" template="layer/filter.phtml"/>
        </block>
    </referenceContainer>

But I get the filter options as per root category.

Can anyone help me to achieve this functionality for custom brand page?