Take out half the tobacco and replace with weed. Smoke the first half anywhere where you think people probably won't smell it (Walking down streets that aren't busy or in a parking lot always works for me. Anyhere where people can see and not smell) then put it out.

Your second half will have resin all over it, but resin doesn't smell too much like weed, and is usually covered by the smell of the tobacco. I've smoked resin cigs at subway stations (with cops and security present), and in front of friends who aren't 420 friendly.

I haven't, and never will do this in front of my parents, however. In my younger days my parents caught me smoking weed several times and not much happened, but I still remember the day I accidentally admitted to my mom that I had smoked a cigarette (Not even that I was a regular smoker, which I'm not. I told her I had smoked 1 cigarette! And I was 17). I thought I would die that day.