Spot on GF.
I have always done the same as you suggest. If you have a third 'standby' altimeter, you can always leave it on QNH until you are through T.Alt, in case you need a quick check on your altitude after you've set STD.
One small nerdy gripe: My understanding is that 1013.2/29.92 is not 'QNE', it is 'Standard Altimeter Setting'.
QNE is the reading on the altimeter when you are on the airfield with STD set. In other words, QNE is the pressure altitude of the airfield.
I've never used it but apparently its purpose is that it may be used at times of very low atmospheric pressure when it may be impossible to set QNH. The airfield broadcasts the 'QNE' and you set 1013.2/29.92 and add the procedural heights to this value in order to fly the approach (I think). Has anybody else come across this?