Drilling a hole is a last resort, IMO. Although if done correctly and in certain area you'd never be able to tell a hole was drilled as the manufacturer has access holes throughout the entire car with black hole plugs covering them, which is the same thing I'd do [if needed]. Yeah, you can remove a bigger dent with a suction cup [as I have one] but in the 16 years I've been repairing dents; I've only used it maybe twice. Even if you remove the bigger dent with the suction cup, then dent still requires actual pushes [from the backside of the dent] with actual tools to fully remove the dent.
If the OP would post up a photo, I could tell him more about his actual repair process. We now use a glue pulling process that does not require any drilling. The glue pulling process is aggravating but with persistence, you can remove a dent. I don't use this process unless I cannot access a dent from the backside. Actually working the dent [rather than glue pulling] is much faster and a better repair IMO, but then again I am usually working on automobiles that I already have taken fully apart like the headliner, hood, deck lid, etc. so access is not a problem.
In the OP's case, he could find someone to remove the dent by glue pulling or possibly access it thru the sunroof but that would depend on where the dent is.