Kneaditite is one of the names for the two-component epoxy putties out there. Usually the putty you find at regular hardware stores is older and drier than the one you find at hobby shops, but their formulation is pretty much the same.
Depending on formulation, the curing time varies from 5 minutes to a couple hours, with the maximum hardness reached after 24 hrs.
I normally use the quick setting epoxy to shape the basic outline of whatever I'm working, and then use the longer curing one to add in details. I've known modellers that work the exact opposite way, using the quick setting epoxy for detailing, since this way they say there is less risk of destroying by accident what they had already done.