James,
If the surface has actually been penetrated I think that it's going to be hard task for any touch-in repair to be fully effective. I've used Chipex with mixed success - it's worked really well on stone chips on my Tornado Red Golf GTi but not so effectively on my Arctic Silver (metallic) Cayman S. I think that it should work reasonably well on your (flat white?) panel, but it's never going to be good as a full respray.
Take your time, let the paint dry thoroughly before blending in and use multiple coats, as necessary. The great thing about the Chipex kit is that the repair's reversible - just wipe it over with the blending solution.
Good luck..!
Jeff