Use Horz sissors when con is on your 6 and
A Faster than you
B in a slower rolling plane.
You are correct in that useing a horz sissors in a furball can get you dead. But then you were going to be dead anyway, so what do you have to lose?
Horz sissors are designed to make a single faster con behind you overshoot, gives you a chance to get more distance, or turn the fight back into a nose to nose fight.
Key isn't to just keep doing sissors, start small, build em till con gets out of phase, once he is off your wingtip you can complete the turn. He is no longer on your 6.