I had a lot of trouble with drying too much before putting in the jar. Now i hang the branches in a plastic trash bag to slow down the drying in Winter when my ambient RH is very low. I adjust the size of the opening in the bag as needed, until toward the end it's just a 4" hole.
If it is too dry in the jar, add a fresh bud to the jar. There's enough moisture in one un-cured bud to humidify the whole jar. If there's no fresh bud available, a damp cloth over the mouth of the jar, under the lid will work too. There's no substitute for getting it right the first time though, as you definitely lose something when it gets too dry.
While the branches are hanging in the bag I've been using an Inkbird humidity controller to turn on a small fan blowing into the bag when the RH in the bag is above 65, and off below 63, until it's dry enough to jar. I'm working on an automated system that will open and close the bag, and close it completely before the bud gets too dry. Stay tuned for that.