What I would recommend is this: If the batteries are over 10%, let the rotors idle until they shut off. Do this in a SAFE place where the wind for example isn't going to blow the thing over, or secure it to something so it can't move. Do NOT "rev' the motors because the thing is likely to tip and grind the rotors against the ground, concrete, etc. (Especially when the battery is low, the rotors may not all spin up at the same speed, so one rotor might develop lift when the others don't.) While you might be thinking you could have someone hold the thing while you run the motors at 100%, this is a BAD IDEA because it may discharge the battery too fast, causing the puffing that the whole thread is about. So basically, just let the motors run at idle speed with the thing sitting where the wind isn't going to knock it over, or secure it to something somehow and let it run at idle, and keep it level because if you hold it at an angle or tie it down where its at an angle, it will be running the motors like crazy thinking it needs to automatically level itself. You want the motors to discharge it at a safe steady pace.
Below some % the motors will just shut off and you won't be able to power them back on, but the battery itself and the electronics will still be on. Don't try to restart the motors. At this point just plug the thing into your computer and let it sit idle with the motors off (shut off the remote control etc). Watch the battery screen in the DJI assistant to see where the voltage, etc, is at. The individual cell voltages should be close to the same, and you should be able to just leave it there until it drains to where it's providing less than 8.4V total, at which point the charge management unit on the battery (the "smart battery" electronics) will just shut off the battery. If the voltage ever reads less than 8.4V, then you have a bad battery (either cells are bad or the charge management unit is bad). If it's under warranty then send it back for a replacement.
Once the battery shuts off, you might want to let it cool for a few minutes but this probably isn't necessary since it's only been draining at 600mA (at least on my P2V with the camera on. The P2V+ may drain faster even with the motors off. It should really only heat up when it's being drained really fast, such as by the motors running at maximum.) Just plug it into the charger and let it charge until it shuts off, then remove it from the charger. If you want to check it, put it back in the drone, power it on, plug the drone in via usb, and check the battery screen in the assistant. Cell voltage should be almost the same and it should read "99% charged" or so.
Whatever you do, do NOT fully discharge it and then put it in storage or something. Personally, I wouldn't wait more than an hour or so to get it connected to the charger (though it should be OK for more than one hour. The charge management unit is only supposed to drain it at about 10mA when the battery is switched off.) If you think it might be a day or something before you can connect it to the charger for some reason, then don't discharge the thing until it shuts off (that is don't drain it to 8.4V, shut it off manually at 10V or something and that should make it safer to wait longer to charge it.)
While the batteries may be designed to be 'idiot proof" in exactly the same way cell phone and laptop batteries are, a cell phone or laptop isn't going to crash into the ground and destroy itself if the battery fails. So it makes sense to at least learn what looks normal on the battery info screen in the DJI utility so you can spot potential problems before they become real expensive problems. And keeping an eye on things means that you may be able to return a defective battery before the warranty is up.