For Kaufmann paradox the entropy difference between crystal - amorphous. So the supper cooling rate will differ with nature of the material to material. The thing is it should not allow crystallizing during cooling so you should freeze the material in melt stage. Cooling rate may vary fast 100oC/min or more. The slow cooling will be 1oC/min you should allow the material to crystallize maximum. Please see the attachment. Kindly share your experience after completion of your experiment.