A few years ago I bought a pair of 68 cabinets...a Bandmaster and a Dual showman, and it was a toss-up which was filthier. I was in the detail business then, and I did a soap/water/toothbrush clean followed with an automotive Maguiers upholstery treatment. It looked great, but when I mentioned it in another guitar forum, I was scolded for using the Maguiers on vintage Fender tolex. Apparently the chemicals in the dressing can delaminate the vinyl anywhere that there's a seam because the solvents react with contact cement. I didn't have a problem from the one application, but I've never been tempted to use an automotive product again for musical gear. Too bad, because it worked great. I've used Simply Green , and it works, but it takes a lot of elbow grease.