[soybalm]

Put the two channels out of phase to cancel the middle if the solo is recorded in the middle. Mess around with stereo width, the Air plug in.
I used a Waves plug called center that did a fantastic job of wiping out the center like karaoke but it still sounded pretty full. This was a 90s recording too. If you really want to get geeky. There are a few spectral progams that will allow you to quiet down the guitar parts but like PT said, it will take other sounds out. I was able to kill the vocal to the Beatles Michelle without too much damage. It was only in one channel so I couldn't phase it out but because the vocal was mixed so loud, I was able to easily see it as a bright yellow spectral blob and remove it but it took a few hours because I had to learn it and get the job done that day.