Nipple screw heads stripping
So, I have a number of nipples rounding that I want to replace. I got the new nipples and went to replace the old ones, but I found that when I try and unscrew any of the old nipples, the flat head screwdriver is stipping the screw head of the old nipples. I've tried like four or five different flat head screwdrivers and they all tear apart the screw heads. Is there a better tool for this or different technique? These nipples are probably pretty old, like maybe 10-20 years old.