What's not to get?.....Your dad was telling you that he had done everything you were doing and had tried all the angles on his dad and they didn't work for him either.......
A version of “don’t try to bs a bs’er” :)
Mebbe you neglected to see the part about him saying... "but my boys have heard that line more than once now."
What's not to get about that? Just in case you are having trouble comprehending, it means that he did not understand it at the time when he was a young buck but now that he has grown older and wiser, he now uses his dad's line on his own kids... BECAUSE HE KNOWS WHAT IT MEANS NOW!
Sheesh