Add this to your view.html.php to add the button to the toolbar:
// Get the toolbar object instance
$bar = JToolBar::getInstance('toolbar');
JHtml::_('bootstrap.modal', 'collapseModal');
$title = JText::_('JTOOLBAR_BATCH');
// Instantiate a new JLayoutFile instance and render the batch button
$layout = new JLayoutFile('joomla.toolbar.batch');
$dhtml = $layout->render(array('title' => $title));
$bar->appendButton('Custom', $dhtml, 'batch');
and put this into your default.php:
<div class="modal hide fade" id="collapseModal">
<div class="modal-header">
<button type="button" class="close" data-dismiss="modal">×</button>
<h3>My modal window</h3>
</div>
<div class="modal-body modal-batch">
</div>
<div class="modal-footer">
</div>
</div>
to display an empty modal window with the heading "My modal window" when you click on the batch button.
You can see how the modal window for the articles view is build at /administrator/components/com_content/views/articles/tmpl/default_batch.php (but you probably know that already)