Hello,
I am working with Ferret and acts_as_ferret.
I have 9 different models that I am using for my search capability. acts_as_ferret is working beautifully when I do searches on a specific model.
The problems come when I try to do a `search all` function.
Check these posts, Ferret Pagination in Rails - igvita.com
http://www.railsenvy.com/2007/2/19/acts-as-ferret-tutorial
http://www.frederico-araujo.com/2007/9/6/multi-search-with-ferret
i think it would be easier to modify their versions to match yours. 
good luck
in one of my apps I did this:
<pre> def search if params[:search_article] && params[:search_article][:q] != "" limit = 20 order_by = "title ASC" @articles = Article.full_text_search(params[:search_article] [:q], limit, order_by) order_by = "first_name ASC, last_name ASC" @users = User.full_text_search(params[:search_article][:q], limit, order_by) order_by = "first_name ASC, last_name ASC" @birthdays = Birthday.full_text_search(params[:search_article] [:q], limit, order_by) else @birthdays = @users = @articles = flash[:notice] = 'No fue encrontrado nada con esta criteria.' end end </pre>
model code:
<pre> def self.full_text_search(q, limit, order_by) return nil if q.nil? or q=="" results = self.find_by_contents(q, :order => order_by, :limit => limit ) return results end </pre>