Self-adhesive foam weather-stripping applied at the front edge of the bench can provide a forearm-friendly barrier for both ferrous and non-ferrous parts.
If you don't want it on the bench all the time, apply it to a thin plastic strip that can be laid down when needed and removed when not.
Do your work on a soft, tight-weave, light-colored fabric so that small parts won't bounce if dropped. An old baby blanket works well as do the newer micro-fiber cloths.
For jobs where springs or clips are likely to "jump out", do the work with the work and your hands inside a transparent plastic bag. Clothing bags from dry cleaners work well.