I have a pretty heavy NIC burn rate, so I DO do a lot of bottles, and thanks for asking @FL_Vaper. PLEASE remember, this is just MY method.
Quite a while ago, I had a VERY unfortunate “INCIDENT” wherein I was breaking down a few liters of NIC, into smaller bottles, left 1/2" or less headspace. For reference the NIC had just come out of the freezer, and as I worked through the large amount of smaller bottles it was slowly warming. I was capping them off as I went. Got almost done and heard a popping noise, didn’t know what it was, continued, heard another pop, started sliding bottles around to see what was what, and two bottles slightly “chinked” each other, and one broke (under pressure). Thankful for goggles and gloves. EVERYONE should use gloves/goggles when breaking down.
It became OBVIOUS the the “rumors” I’d heard about PG NOT expanding/contracting were NOT true.
From then on out, I started leaving MORE headspace, maybe 3/4" or so, and because of the increase in air, I grew concerned, researched, and started topping off all bottles with Argon gas. The gap (headspace) is critical IMO to PREVENT over pressurizing the bottles.
This doesn’t have to be complicated, or voodoo witchcraft, and some may think this crazy. I’ve got a LOT of gallons on ice, and have it down to a science now.
I would RECOMMEND at least a 1/2" gap, and topping with Argon.
Hehe, it’s how some shippers send their NIC. Simply fill, gas, cap, then a few wraps of electrical tape to solidify the cap seal. Just prevents any loosening, etc. Maybe for show, but I do it all the time now.
Not really, but I do wash with hot soapy water, thoroughly rinse, then dry before filling.
Hope that helps, and I strongly recommend reading my little “incident” above, in regards to the need for a gap/headspace in each bottle.