the key to double flaring is having a good tool. I bite the bullet and bought a hydraulic flaring tool with 45 and 37 degree dies. I can tell you that once you get a little experience, you will make flares that look factory.
On my 52 pickup, I ran hard lines from my transmission to a bracket just under to the left of the oil pan where I made a bracket, then went with flexible lines to my cooler. On my challenger I ran SS braided all the way from the trans to the radiator.