Trying the it is too hard will prove an almost impossible task. Heat your hands on a radiator or rub them together and roll the substance in both hands for several minutes. and DIYers who do not soften prior are faced with a much more difficult process.
Most of what I read says around the bottom of the sink strainer between the strainer and sink. My sink strainers came with an almost foam like gasket for on top (for underneath there is a rubber gasket).