Feree Tool Co. makes a slide hammer with a hook that fits the inside curve of valve slide tubes. This tool is what most techs use for this job. For the main tuning slide a grooved wooden block that is shaped for the individual tuning slide is then hammered with the very light blows from a very light hammer. There are many solvents that will help to release the corrosion that has formed between the inner and outer legs of the slides. Again, Feree Tool Co. makes these solvents available. Most penetrating oils work well with feric oxide,( rust ), but are useless in penetrating cupric oxides, like those formed in uncared for slides. The old saying that "an ounce of prevention is better than a full pound of cure" is the motto here. GREASE those slides and you won't have to fight to free them up.