Well as its 2 pack if you have mixed it in the right proportions, within 48hours or less it should of gone off, but it depends on temperature and if you used any accelerator and what hardener. So assuming its been 48 hours (its most likely going to absolutely fine sooner, but 48hours plays it safe, also do the close up sniff test, if you can still smell it, its still going off). Start flatting and polishing to your hearts content just do all your flatting wet with some soapy water.