<%= simple_nested_form_for(@foo) do |f| %>
  ...
  <%= f.simple_fields_for :bar %>
  <%= f.link_to_add :bar do %>
    Add bar
  <% end %>
<% end %>

<%= f.simple_fields_for :bar, :locals => {:baz => 'baz'} %>

<%= baz %>

<%= render partial: "my_awesome_partial", locals: {variable: 5, baz: 'baz'} %>

<%= f.simple_fields_for :answers do |answers| %>
   <%= render 'answer_fields',  { f: answers, question: @question }  %>
<% end %>