My experience with lead has lead me to use it only at-or near-the edge of a panel, or a factory seam. Using it away from the edge or seam, is just too much heat, and leaving you always needing to add a little more lead because of shrinkage in the metal beyond the end of the leaded area, like a dog chasing his tail. The extent of that depends on the crown of the panel, of course.
I tried lead on the filler panel between the trunk lid and back window of a mustang a couple of decades ago, to get the seam level, but it got too hot and it ended up lower than before. Had to remove and replace the panel, but when doing a different mustang recently with the same problem, I just used a jack to raise it up to level. Over time it might drop again, so I'm thinking it may need a little support to be sure it stays in alignment.
The point being that lead is easy if you know the pit falls, such as cleanliness, proper tinning, and correct amount of heat, to name a few. There is a learning curve for sure, and utube is not the place to learn about lead. I have the video that Chris mentioned, and it is good. Here is another one that I like even better.
https://www.tinmantech.com/products/dvds/autobody/The-Art-and-Science-of-Autobody-Soldering.php
