Whoooa, I see I lit a fire in here.
I agree with Kultulz one hundred percent, I use a propane torch opened slightly and I move it around. Since it is regulated already it is very safe, The worse I have seen happen is the torch gets accidently lit when it meets a spark (cracked spark plug wire). The volume flow is so low that accumulations are hardly a concern and with the vehicle running there is air movement anyway.
A simple propane torch is all I use and so does most factory shops I've been to, as for calibration it does take a special regulator setup to do properly. I have never used one because a simple propane torch works just as well although not nearly as scientific.
“She may not look like much, but she's got it where it counts, kid. I've made a lot of special modifications myself.”
— Han Solo