If you're getting stainless lines, the stainless is a little harder material. When tightening with a line wrench, I found it best to tighten the nut and then back it off, then tighten again. I did that 2-3 times per connection in order to get the flare to seat.

I replaced the entire braking system on my 67, so there was no fluid at all in any of the lines. I first bench bled the master cylinder, then mounted to the booster and hooked up all the lines. I then filled the master cylinder to the top, and then cracked all 4 bleeders and let gravity do its thing. I let it sit overnight like this. The next morning I had fluid at all 4 corners. I then closed all the bleeders and then bled the brakes the traditional way. Made 2 passes around the car and had a nice firm pedal.
This method worked great for me. I didn't need one of those pressure or vacuum tools.