I find 20 min soak in hot mildly soapy water will tell me which labels have water soluble adhesive, which are the acceptable kind of gummy and which are the PITA kind of gummy, and which are plastic labels that can be peeled once they've been softened up a little by the heat... After I've taken the bottle brush to all the insides, I use a spoon to scrape the labels off (I find the curvature of a spoon works better than flat knife) and then sometimes the bottles go in for another soak if required, especially by the time the water's cooling off, as I make this an all day process while I'm doing other things, the bucket I use fits 7 standard wine bottles quite neatly and I can get a couple cases of bottles done in a day without really feeling like that's all I've done all day.
I use a plastic pot scrubber to remove remaining water-soluble adhesive & label and the acceptable kind of gummy labels (like the packing labels I use for my own labelling) that didn't come off with the spoon. I find this works well for most adhesives. The real tenacious PITA gummy labels that won't come off nicely with a soak and a scrape gets the Goo Gone treatment in a box on the other side of the basement, I don't particularly want that stuff making it into the air around my airlocks or gettting onto any of my equipment.
Then anything that had to be treated with Goo Gone gets a wash with dish soap to get the chemicals and any remaining gunk off... Now and then I run into a label I can't even scrape or peel off, and it goes in the "Take it Back" box for my $.15 at the Beer Store, sometimes they're just not worth the work.
"The main ingredient needed is 'time' followed closely by 'patience'." - The Bishop 2013
"Good grief! If someone wanted to murder you, all they would have to do is ship you a 55 gallon barrel of honey and watch you document working yourself to death!" - Vance G