Jar the product, along with a Caliber III hygrometer. One can be had on Ebay for ~$20. Having tested a number of hygrometers - digital and analog - this model in particular produced consistent, accurate results. Then, watch the readings:
+70% RH - too wet, needs to sit outside the jar to dry for 12-24 hours, depending.
65-70% RH - the product is almost in the cure zone, if you will. It can be slowly brought to optimum RH by opening the lid for 2-4 hours.
60-65% RH - the stems snap, the product feels a bit sticky, and it is curing.
55-60% RH - at this point it can be stored for an extended period without worrying about mold. The product will continue to cure.
Below 55% RH - the RH is too low for the curing process to take place. The product starts to feel brittle. Once you've hit this point, nothing will make it better. Adding moisture won't restart the curing process; it will just make the product wet. If you measure a RH below 55% don't panic....