I've never done it that way, but if I were to do so here's the game plan I'd implement. Push the grommets out towards the outside of the frame just enough so they no longer protrude i.e. they are flush with the inside of the frame (obviously the frame is unstrung). Then apply the lead tape securely, and smooth over the surface. Use an awl to poke holes through the lead tape. Then push the grommets back through to their proper place. Finally clean/smooth the lead tape edges especially around the holes.
Again, I've never done this before. So attempt at your own risk..