The first lesson in Trimming 101 is: don’t use the same beard trimmer you use for facial hair on your pubes. A ball trimmer designed for manscaping won’t have the same functionality as a beard trimmer or clipper.
Choosing an electric trimmer for grooming body hair is a big choice since they come in all sorts of designs. Be sure you choose one that is kind to your balls. Advances in technology like the SackSafe blade, cuts through coarse hair, without leaving any nicks or cuts.