Supersheen and it's close relative AcrylGLOSS are acrylic resin paints that work very well on inflexible surfaces. However, it was never designed to be used on "bendy" surfaces such as leather. It is cracking because the flex in the leather is fracturing the emulsion of the paint.
A much cheaper, and more effective method that will avoid dye transfer is to apply a very thin wax coating to the surface of the item. By this, I mean boot polish. I use neutral boot polish applied with a duster wrapped around my finger and rubbed in, or for larger surfaces, a boot brush. Let it dry for five minutes then buff to a shine. Repeated applications will enhance the shine, but a single application will seal any dye and prevent transfer to clothing etc.
If you need an alternative that will give a permanent shine with no further intervention, then one of the leather treatments such as
Resolene A water resistant top finish for leather. Available in neutral and black.
Resolene can be purchased from
Le Prevo leathers. Give them a call, they are very very friendly and can give additional advice.
Eric