One question that needs to be asked is how deep are these pits and what size are they? If they are only very shallow and not very big in size then any mixture is going to struggle to take hold for very long. Most of these metal-putty compounds require a reasonable (relative) area and depth to get a good grip. They may hold on initially but I would suggest that after a while will fall out. Undercutting has been mentioned and this would be very helpful and would most likely make the putty stay in regardless of the size of the pit. The problem is doing the undercut. The chamber has a diameter of 0.574" (14.6mm) at the entrance to the chamber which gets smaller towards the mouth and the pits are half way along at 1.5" inches. This would make undercutting extremely difficult and at best you would only be able to access one half of the pit. Undercutting really requires you to be able to access the affected area at right angles so that you can use a very small ball nose or dovetail cutter to remove material.

Micro arc may work as you could bend the electrode into an L shape after grinding the pit to a more open shape. I have had to do this on jobs myself although on much bigger jobs. The restrictive area to work in is going to be the biggest problem.

Matt.