well for shaving your balls, use a regular disposable safety razor. the cheaper 2-blade ones are actually better because they will result in less irritation strangely enough.
Unless you have ball-hair as thick as your face, it won't take many passes to actually remove it off your sack, 2 blades going over your skin will irritate less than the modern 5 blade razors (I would go into it, but I would end up blabbering fake razor science). Plus they are cheap for disposable 2-blades. Just make sure to 'prep' them first, warm shower, clean them, spend at least 5 minutes with water on you before lathering up for a shave. pull the skin tight and shave (you wont cut yourself at all if you pull the skin tight, trust me)
This is similar to what I shaved with this morning (WWII era twist to open gillette and Derby stainless blade / badger hair brush / cella shave soap / witch hazel rinse / bay rum)
Balls? use a can of foamy and these