Need 2 shipping methods, 1 flat rate and 1 by weight

Hi there,
I am new to Zen Cart and after researching for many hours the FAQs and forums I cannot find what i'm looking for. I need to have two shipping methods. First is a flat rate for our gift cards (no limit on quantity). Second shipping method is by weight (for t-shirts). I do not want the flat rate to show up when ordering t-shirts. If customer is ordering both a gift card and t-shirts, then I would like for the by weight shipping method to apply.

Any help is greatly appreciated!

Are the Products that you are calling Gift Cards the same or different from the built in Gift Certificates?

If they are different, how do you identify your Products that are Gift Cards from other Products?