Removing glue from old HO models

Any tips on how to remove or unglue old HO models (50's and 60's)-some have a brown glue that is not easy to soften-any ideas without ruining all the good prepainted and lettered sides. So far I have separated with Xacto knife and then sanded but glue sometimes will not allow this approach without danger of ruining other parts.

maindefer I am sorry to say that I have as of yet never seen a dissolver of certain types of glue that was effective on the glue without damaging the paint.

There isn't really much on the market at present to remove glue from loco bodies that I could recommend. Lightly sanding the surface of the glue can weaken it and leave it open to removal with beeswax polish but beware of glue over decals and printed details. A Beeswax based spray household polish will sometimes disolve glue on loco bodies but it won't completely do the job. It's a painstaking job to do alas and results range from near perfect to average. Surgical spirit is also good on old glue but beware of certain plastics and it will remove paint and decals and should only be used on body coloured locos(i.e. the colour of the plastic the loco was moulded in). Cousins Imperial Leather Soap and some water can also soften old glues helping with their removal. Which ever method you choose, it's a long haul and will take several hours to get a satisfactory result. The keyword is patience.