Thank you, Frederik. I've skirted through tensors in the past but never had to put them to use. I don't see a great mystery there, though, just a problem with severe rust and little fluency. The real issue is that a great deal of language (developed along with the math or because of the math) has developed in relativity that applies to qft. In what I've worked through, I'm using the symbols without understanding what they really mean so I find that I am off in the weeds quite often. I have so many gaps to fill in and it's not that I've forgotten the material (although I struggle to remember lots of things), its that I've never covered the material in the first place.
Maybe weinberg is a good way to be sidetracked for a while. It will take a little work to tell.
rgds - Mark