Ramps and/or pins are nearly essential to have brifters work. What I do to get old rings to work with them is to file ramps on them manually with a small file. Angle them so the new "flat" is directed to where the chain comes off the next lower ring. It works great. A small "flat" gives the chain enough purchase to climb up to the next ring easily.

I have made all sorts of size combinations work with just a little work with the file.