Get yourself a microwave just for moisture testing, and find a place for it outside of the house and well ventilated.  I don't mind being around one, but it can get kind of rank for those who aren't used to it.  Get a lab quality scale or an electronic postage scale that will weigh in tenths of an ounce.  Keep them just for testing samples (and maybe heating up your lunch if you aren't the fussy type).  You test a sample of whatever you want to know the moisture of; grain, silage, or hay.  You need to shell off some grain if you want to test for combining.  Anything you are chopping, the best results will come from grabbing a handful out of the chopper.  It's hard to get a good sample by hand for forage unless you chop a whole plant by hand.