Horrible Paint job, and how to proceed?

[LagunaGlide]

My '70 has been resprayed I would guess at least 3 times. The top layer on the truck now is absolute crap. It is chipping, cracking, and flaking away, let alone the worst of the colors below. Today I tried Easy Off, and it was a pretty pointless venture.

Bottom line is, I want at the very least the top coat and it's primer gone. I would really like to get it back down to the original color and go from there. If the truck is going to be painted again it's all going to have to come off anyhow.

I can fairly easily take a razorblade and cut down to what I believe is a layer of primer (eggshell color) on top of the original paint. That eggshell colored layer is difficult to get under without taking up what is under it.

I don't know a ton about paint, and have thought about continuing to remove as much as possible with the razor, but can't help but wonder if a wet sanding will be faster, or how coarse of a grit I can use to make the process faster.

The pics below show the layers.