I think our ancestors would have used anything that came to hand. We always base our assumptions on what we would do in the present and try and explain it to what was done in the past (ethnoarchaeology). I studied flint working and related tool use (ancient and modern) during my University years. I looked at it from the perspective of the user and scientist, investigating the objects themselves i.e. how was it done. I used to trawl through endless papers on the complex physics of flint knapping and re-touch etc. Most of it can be explained with equations and mathematics to the point of obsession but it is the practical that really brings it to life. I have hardly every come across any copper objects within the archaeological record and the ones I have found are usually decorative rather than domestic functional. If I found a stump of copper, the odds of the handle surviving in the burial environment are remote. It would be passed onto the so called 'specialist' to stick it into some 'ritual' based collection to be lost in the museum archives. I had a colleague who studied ancient antimony in copper weapons. These were discovered in a Russian museum. The weapons produced were located from one source in an ancient burial. The copper weapons were spears and swords. After a detailed evaluation of the composition of the copper it was discovered that they were far too soft to be used in combat. The conclusion was, they were either ceremonial or used specifically for laying with the dead. Their original weapons were then re-used by the living.
I think in prehistoric times it would have been possible to carry a copper tipped implement to bash at the flint, but I cannot see it lasting that long. It is bad enough trying to chop wood with a copper axe never mind trying to flake flint. But I base this assumption on what has been found in ancient Briton and the composition being reproduced. There could have been tools that were very hard to the point of being used as general tools but we are as yet to find them (or by the time our ancestors did the technology had moved on).
Working with flint and related materials is no magic art, there are many archaeologists/anthropologists whom I know who can rapidly turn out beautiful Acheilian hand axes that could have come from yester year. Its just a matter of knowledge of the product you are working with, patients, practise and a good aim.