At Christopher said in his answer, there isn't any shortcuts to become a shredder. It need a lot of practice. You need to practise picking techniques, fretting hand techniques, three notes per string scale patterns, sweep picking, legato, tapping, artificial and pinch harmonics, scales etc. That is a fact which doesn't change whether you are learning with GT or some other resource. Guitar Tricks have lessons for all of these on Styles of Guitar section. Using a metronome is recommended when practising and developing speed. You can find metronome on GT Toolbox section, if you don't have a physical one.
If you like to practice shreding by playing songs here are some
Pachelbel Canon In D Baroque & Roll
