rharv,

He can't use the PG plugins - it's a movie editing suite that uses VST plugins.

This will take you to all of the free VST compressor/dynamics processors on KVRaudio.com's database:

http://www.kvraudio.com/q.php?search=1&ty[]=e&f1[]=vst&tg[]=23&pr[]=f&av[]=re

I recommend the products from Gvst for simplicity as well as visualization of what is happening to the signal.
http://www.kvraudio.com/product/gcomp_by_gvst

Also, any product by this developer; platinumears, is very worthy of your interest. Here's a multi-band compressor which you might find works even better for your application:

http://www.kvraudio.com/product/5orcery_by_platinumears

-Scott