Not everybody has a MIG welder in the garage. Here is what I'd do if I were in your shoes. Taking the trunk lid off is a great idea. It will be easier to put filler on a surface that can be positioned to be parallel with the ground as opposed to perpendicular to it. Grind around each hole with 80 grit about 1-2 inches out from the hole. Then, with a small ball peen hammer, tap each hole so that it is indented a little. Put a piece of tape on the back of each hole so that the filler will not go through the hoe. Stand the trunk lid up so that the part with the holes is parallel to the ground. Mix up a little bit of filler at a time and spread it over the indented holes. You are far better off mixing up small batches and only doing a few holes at a time. DO NOT USE REGULAR FILLER NOW. It could crack / pop out eventually. I'd use an All Metal filler. They go by different names, but any store that sells body work supplies will know what you mean. All Metal type fillers have a high metal content. They mix and spread like regular fillers, but they will be much more resistant to shrinkage and cracking. Then sand and finish off as normal. You can use regular filler for the final finishing now. Done properly, this repair will last a LONG time. Before I had a welder, I repaired holes like this all the time.
