That's what I hate about digital multi-effects , you're definately gonna waste some serious time to get the right tone that matches with your amp.
The most important thing you should learn first is how to change the parameters of each effect , and how to save your setting... I think that there was a small (couple of pages) pamphlet that comes with Boss products called Turbo or Quick Start , read it thoroughly.
From my experience with my GT-3 , I say experiment with the factory set patches first , then do the fine tweaking till you find your optimum tone and save.
The better (harder) way is to make up a patch from nothing , but it's gonna be hard & time consuming since you've got lots of options & combinations to try first.
I've found a lot of GT-3 & GT-5 patches online , and I can tell you that you're not going to find what you're looking for , because of the different amps and so ... I recomend that you waste time with your GT-6 and learn how to get the most of it , instead of wasting your time searching for patches (that you'll eventually don't like) online.