Multiple model search with acts_as_solr_reloaded

I have used act_as_solr_reloaded plugin for searching option in my
I have two models which are brand and sku and its association are

class Brand < ActiveRecord::Base
acts_as_solr :include => [:skus],:fields =>

class Sku < ActiveRecord::Base
acts_as_solr :include => [:brand],:fields =>
=> :date}]

I should form conditions from multiple models like‘true’ and'true and
and between ‘from date’ and ‘to date’

I am really struggle with date range search.
please help me how to make search like above using act_as_solr_reloaded