Slow down your speech some, ie when responding with "yeah" make it go "yeahhhh". Go monotone and avoid pitch changes, make your voice sound like Kansas, flat, low and rolling on forever. Throw in a lot of words like "dude", "bro", "man" (as long as you're not talking to a trans femme person). Play with softening words a little, don't enunciate as well as you used to (ie say "wurs" instead of "words", "cah girl" instead of "cat girl", as if you've had a beer or two. Try to move sounds you would normally make at the front of your mouth like "S" and "T" back a little into the mouth by positioning the tongue on the front roof of your mouth rather than at the teeth. Smoking is a nasty habit, but it can thicken the vocal chords and drop your natural tone in a few months if it's something you can pick up and put down as you want. Hope any of that is useful.