Hay smell comes from several sources ;
1. Harvesting too early ( buds not fully mature )
2. Over drying ( chlorophyll not degrading and " locked " in )
- even with curing methods , buds may have past the point of no return. Rehydrating will not start curing process again.
3. Chemical nutes = Flush every time. Force your plant to cannabalize itself for the stored nutes it has within itself during final weeks.
Control the time and conditions ( of your OWN drying area )
Everybody else's suggestions work for them , but may not work for you. Some areas will dry too fast , so you have to check them far more frequently. For me , I barely get 3 days before I got to bottle up. BOVEDA PAKS work well to stabilize RH.
Here is the trick :
Dry up to the point of stem " Near " snapping. It is far EASIER to bring down moisture level within bud than
to " rehydrate " OVER DRYED BUD.
Once to cross over into OVERDRIED , it's too late.
To check moisture in bud :
Bottle up buds with hygrometer 24 hours. Check after 24 hours and check reading. If over 70% - pull out buds and dry on cardboard or paper towels for a few hours . Re bottle and check in 8-12 hours. If humidity dropped , you are on right path. Burp once a day , until you incrementally drop to desired level - some go for 62-64% or to 55% ( as some prefer ) ( more drying for this ).
Brown bag : large brown grocery bag , not white bags ( they are bleached ). Toss in around 4-5" deep of buds . Roll top and store in dark cool place . 24 hours later roll bag back and forth to distribute buds , don't open . 24 hour later after that , open and check buds ( moisture level within ) and either bag up again or bottle.
BOVEDA PAKS is a cheap way of maintaining basic RH in your jars.
CVaults is another product I use to " cure " and has cut the bullshit with normal methods. They let absolutely no light in , airtight and stay cool ( stainless steel ).
Make sure you are chopping at right time , not too early.