by the time I've switched back and forth from DIN to yoke for various uses, and since I'm not completely switched over to DIN because of tropical diving and tank rental. I've done it on tailgates of trucks, on boats, etc.
I've never used a torque wrench. I've never seen a torque wrench in a scuba tech's shop, and I've seen several shops. I use the "L" shaped allen wrench to intall the DIN kit. Like someone said above, snug them down and then put a little torque on it. You just have to snug down the face Orings, you aren't depending on threads for a seal. I wouldn't use any sort of leverage.
On the other hand, I'm used to mechanical stuff and got over a long time ago the "tighter is better" mentality. Ever strip out a spark plug in your car? You're torqueing it too much! I used to use torque wrenches for auto mechanical do it yourself, but not after I got used to various torques, uses, and materials.
It would be possible to strip out brass threads fairly easily. If you aren't comfortable, let a shop do it. I guarantee they won't use a torque wrench.
By the way, I've never had one leak or break.