Removing the old paint “edges”

Applying simple physics to sanding means edges will only go away by "leveling"-filling in or grinding down.
Pardon the ignorance, but I didn’t know anything about the blocks. Im sure I seen them in videos but just didn’t snap to their role. Now I’m thinking the dura block approach may make small work of this.

The Eastwood video too looks like using the combination of durablock and body filler may help things. I have been very conservative on the body filler to avoid a “Bondo” car. But maybe part of my issue is being to conservative with it. Think I might order a couple of them blocks and take another stab at it......