Dino,
I’ve read here where others have “center punched” and more often than not, the porcelain chips since it’s so brittle. I feel it’s really not necessary. I used a 1/16” very sharp drill bit in a variable speed drill, steady the drill bit against the porcelain with the middle/ring finger against the grill/smoker and the thumb right next to the chuck on the drill and started off very slowly, 3 revolutions/second or so and increased speed from there. Keep the drill bit perpendicular to the porcelain surface and you should have no wandering. Install a larger bit, 1/8” or so that will accommodate the smallest size of your step drill bit (Unibit) and enlarge the hole. I think the key is like you said ~ Light to moderate pressure and slower speed. I believe the tape also helps.
Bill