The only one talking nonsense is you.Nonse
Nonsense, Lechler 29107 is specifically an automotive product. I go from 320 dry through the grades to 800 dry. Never have I had to put any unexpected effort into it, although it is clearly not as soft as conventional primers.
For me, the whole point of epoxy is to get away from conventional primers. If you want to use them, it is your business. I just don't see the point in holding so many different products in stock.
Try reading the data sheet for the product you swear by and you will see you're not using it as recommended.
I've said my piece, I'm not getting into an argument with you.
I'll leave this thread there and wish the OP success with his rework