here's a tip from an old leather worker who does it the "same old way".. Buy a pumice stone and you can abrade, or in your words, "take the gloss off", the skin side of your leather so glue will adhere to it.
pumice /pŭm′ĭs/
noun
A light, porous, glassy lava, used in solid form as an abrasive and in powdered form as a polish and an abrasive.
yea I know I have used the stuff, I've turned my share of wrenches. Pumice comes from volcanoes and is very aggressive on skin, leather is skin. The pumice will damage it. if you don't believe me go wash your car with it. Its not a guess its a fact google pumice then use some common sense and ask yourself if you think it will damage leather.