I'm totally lost... like seriously.
Assuming that I use M instead of E, If I have an edge at UFl (sorry, I don't know the correct notation) and the one to be paired at UBr, then I would do:
r' U' R' U r
and then look for the next one. Is this a bad way to do it? In this case I am "storing" in the R layer
Yes. First of all, that is single edge pairing.. No one does that, it would be silly. Also, don't use UBr (or UFl for that matter) for the buffer, that is also silly. My main problem with calling it storing is that unlike.... say freeslice 5x5 edge pairing, you generally don't care about what is in the slice, unless you are purposely keeping them filled. The only edges I would really care about keeping filled are on the U and D layer, but you would say that I store in the R and L layers. I get what your point is, I just don't know if I would call it that. It isn't the same as what you would do with freeslice 5x5 pairing. If you question was worded something like "which layers do you use to insert unsolved edges from", it would have made a little more sense to me. 4x4 edge pairing is usually much more free and solved edges can generally be "stored" anywhere no matter which slice you use for pairing.
And Vault.... okay okay...
You're still sneaky.