Copper Flare Fitting

The stove in my RV has a flare-fitting on the end of the copper pipe. When I reconnected it, there was a leak. I read some stuff online about not over-tightening, but I was not tightening enough. A friend came over. He added some pipe dope with teflon to the threading, being careful not to get any inside the pipe, then used two wrenches to tighten the nut against the fitting. That did the trick: no more leak.