How can I seal self drying clay so that it will not crack?
Can I paint it with acrylic paint?
Usually when clay cracks it means the drying process is too fast. You can try to slow it a bit by putting the object in a more humid place.
Even with a self drying clay, you need to watch that thickness. I wouldn't try it any thicker than 1/2". The thicker it is, the more it will tend to crack.
Always keep it's humidity, for example, spray water every day will do.
Better use some plastic bags to cover it(Plastic tablecloth will be good)after you sprayed the water.