This trick is easy if you have songs from the original Rock Band transferred to Rock Band 2. If so, choose "Wave Of Mutilation" from the Pixies and play the song with the Rock Band (not the Guitar Hero) guitar. The solo is only around fifteen notes and are orange and blue. Use the solo buttons to play them.
Play the song "Give it Away" by Red Hot Chili Peppers. There are three solos, and the first one is very simple. Just play on the solo buttons from the start of the song until you get to it.