Most gloss finishes can be knocked back to satin using extra fine grade (0000) steel wool or synthetic equivalent (which is a much less messy option.)
If you have any dedicated woodworking stores in your area you might consider a product called Mirlon, it is a synthetic pad and comes in 2500 & 3500 grit, it will work very well.
But you might want to double check the type of finish you have on the guitar. If it is nitro then you can easily polish back to gloss later should you change your mind. If it is a polyurethane that might not be possible.
If Mirlon is anything at all similar to Micro Mesh, it's the best stuff on the planet. MUCH easier to go slow and watch what you're doing without going too far. Also, if you purchase a kit they have an assortment of extremely fine grits which will basically allow you to "undo" your work if you decide you don't like it.