Specifically, I have two httpd.conf files:
/etc/apache2/httpd.conf
/etc/apache2/httpd_2.conf
How should I modify the /etc/init.d/apache2 script so that instances of Apache will be invoked for both configurations?
The apache2 script is currently standard/unmodified.
see https://serverfault.com/a/397236
alternatively, is it possible to solve your problem with different vhosts?