Usually if the 2-3 shift is "soft" as you are describing, in most cases even with the adjustment it is too late
I adjusted mine as soon as I got it home and it failed about 2 months after on only my 2nd run on the highway. Previous to that, it also had about a 2 second delay. As for your fear of an air pocket, it is nonsense, that is not going to be an issue as the transmission actually has "vents" on it to release any gases-air or water vapor or whatever may enter the system.