well you could try a de=essor if you can dial in the right freq of the squeek, and reduce it without affecting the overall sound too much, the Logic one isn't great on vocals I found, but might work on a gtr. You could also try a multi-band limiter and isolate a narrow band on the squeek, or a freq dependent compressor. All pretty much do the same thing just you'll find some work better than others. Eg find the squeek freq then adjust the threshold so the compressor starts to reduce the volume..I have a nice guitar take, but there's a fair bit of squeak from swiftly sliding fingers. The more I eq the guitar to fit the mix, the more noise!