Break the cam in with your old springs, then swap in the new ones. Make sure you coat the lobes and bottom surface of the lifters with the moly grease that the cam comes with.
Sorry, I disagree. Install the new springs on the head to be used and break it in with the new cam. There is no issue in doing this. The way you suggest is just more work that is not needed. The old springs may not have what is needed to do the job right and once.
The cam is small and doesn't need to be babied or large enough for break in with half the spring set up.