Here is my technique!
I dont go completely bald around my groin, but I do love a shaved scrotum.
What I do is get a used (has to be sorta dull) mach3 razer blade. I shower normally for a good 10 minutes, which makes the sack nice and pliable. I then put soap foams all over the mellons, then I strech the skin flat and go at it. It never takes more then 2 minutes to shave the entire thing. You dont have to worry about getting it all, becuase I do this every 3-5 days, so anything I miss now, I will get back later.
The dull razer isnt as harsh on the sensitive skin, hence I never get ingrown hairs, or anything.
As for nail, I only use that on my shoulders and back. Chest = wax, but that is a rarity since I have a few ugly stretch marks on my abs which look better with hair covering them anyways.