I interchangeably use Triodent and Garrison parts. My go-to is Triodent blue extra curved matrix with Triodent rings, but will use Garrison metal rings if I want to curve the wedge against the gingival margin or the Garrison orange or green ring if I want a different proximal contour.
Looks good and simple, it wasn't. Back to back's are difficult and, for me, time consuming. Keep trying and you'll get better. It is always better to do these one at a time to develop a good contact.