I had this exact same problem until very recently (very recently in fact)
(it was me who finaly resorted to direct nostril vaping off my PV and 'french inhaling') until I could get this sorted.
First I found, you don't do it like smoking an analogue.
Smoking an analogue you'll send it down your lungs, through your system and back out your nose -- that does NOT work much if at all with e-cigs You just run out of vapor way before it gets to your nose)
The trick I finally finally found to this was to
1. take an oral inhale of vapor (only into your mouth then stop right there)
2. momentarily stop and think about it (especially at first) with the vapor still in your mouth (don't try to inhale it in your lungs or try to push it anywhere else)
3. kind of 'prepare to breath' through your nose (but don't actually breathe) open your nose from inside (this really took some discovery on my part to figure)
4. push the vapor up with your tongue (just lift your whole entire tongue up all at once, like its on an imaginary hydrolyc(sic) lift in there or something)
5. at the same time you are doing #4, start to slowly nasally exhale (takes some practice to coordinate)
6. the vapor finally goes out your nose.
Summary: you have to send it straight from your mouth to your nose (no middle lung traveling or anything else)
it takes a bit of oral/nasal coordination I have oral/speech coordination issues so I am still not 100% at this but this is the best way I can explain and the most reliable that I've come up with so far. It took me about two months of 'vaping' in all to figure this out, odds are you'll get it much sooner.
