If you're going to use DBE, select a minimum of 50 points. Radial gradients are from inaccuracies in flats calibration, where as liner gradients are created from light pollution. The following is done on 4 stacked, aligned and calibrated LRGB masters. I hope it helps you as much as it has helped me. So I have deconstructed the tutorial to just the essential steps, skipping all the how and most of the why.
After finishing the tutorial, and running it on a few old images sets, I really liked how the images were coming out but I struggled to remember all the steps.
