I've used clock cleaner for clocks for years, I also used it to clean all manner of brassware. Clocks have some fine parts in them but I've never had a cracking problem though for clocks I use an ultrasound cleaner which does it much more quickly. It doesn't have to be too expensive as you can buy small quantities for well less than £10 and enough to clean up the odd item. I've very recently cleaned a pair of mandolin key blocks using some spent clock cleaner (I keep it in a separate bottle and that's OK for cleaning the odd bit of brass). They were black when I put them in but nice bright brass when I took them out afteran overnight soak.
The art of using it is to wash it off with water immediately you remove it from the cleaner, dry it of as much as possible then spray with WD 40m the cleaner to remove any dampness. Never leave it laying around with cleaner on it, it will remove the zinc from the surface and leave it looking coppery.