To he fair, sometimes "dual fueling" can help.... I get where your coming from with the "pick a day" to quit the fags, but to be honest that's not going to work for everyone.
If you smoked 10 a day, but since you started vaping your down to 6 a day, that's 4 fags you didn't smoke, so your on your way to quitting smoking....
For some of us, quitting the fags and vaping full time worked (it did for me) but I know for others it hasn't, and they've gone back to the fags as they've felt like a failure .
Do what feels right for you....you'll fund your right balance.....and soon enough, you'll realise that you wont want a fag at all....
Good luck!