You need more than just brushes to clean out those lines, unfortuantly whirlpool tubs harbor lots of micro organisms which can lead to big time problems. Major reason is cause the piping beneath the tub still holds water even though the tub its self is drained. And folks don't use them often enough to flush the gunk through. This link will explain in more detail:
http://www.sanijet.info/faq.htm#3
So, best thing you can do is to order some flush to clean out the lines and ensure they're safe again. I've ordered many times from the following company and have had great service with them. Here's a link to what you'll need:
http://www.spadepot.com/Merchant2/me...de=Maintenance