I too found vaping very harsh in the beginning. There is definitely a technique to it like Glock Rock mentioned.
I find that the best method is to take a slow deep pull. Don't inhale it yet, just let it pool into your mouth like a cigar. Once you're done pulling, then open your mouth and inhale. That works best for me.
Do you have the same setup as your son? Try to provide more information on your setup. Are you using a cartridge or tank system?
I ask because I started and still us a
DCT on an
ego 650mah batt's and at first I noticed that the
cartomizer wasn't wicking right (absorbing the e-liguid from the tank) and learned that a couple dry pulls (pulling without activating the battery) helped draw liquid in.
Regardless it was still harsher on my throat than a cig, so I was doing as 440BB mentioned.
Once you get that burn in the back of your throat, any vaping seems to burn for some time. It makes it hard to tell if you are still causing it or it's just raw. Small short puffs and a lot of water and you should be in a better position to feel it in a few hours, definitely better by tomorrow morning.
After a few days, as many told me, the harshness did go away, but during that time I did have some cig's to fall back on. I may have smoked about 1 cig a day those first few (4 days to be exact) days and I distinctly recall that last cig that I lit up. I couldn't finish it, maybe took 3-4 drags, and tossed it cause it was just nasty. If possible please tell us a little more about your set-up and I'm sure you will get better advice and info to help your experience out. Never quit trying to quit the cigs though and this is a very viable means to do so. The only one that helped me as I believe I was more addicted to the action than anything else about the cig's. BTW former pack a day smoker.
