I have a S&W 929 that takes moon clips. In fact, they are required for the gun to work at all. The cartridges do NOT headspace on the case mouth in this revolver. If dropped into the chamber without the moon clip, they fall way too far into the chamber to fire. There is no ledge in front of the chamber for the case to stop against.
Once you get the moon clips and the appropriate mooning/demooning tool, you will find it isn't any worse than loading a magazine for a semi-auto pistol.