How do you get stealth Camo in Metal Gear Solid 3

There are two different ways to obtain the Stealth Camouflage in Metal Gear Solid 3: Snake Eater or Subsistence (doesn't matter which one).

1) Shoot all the Kerotans (frogs)

I don't recommend this one. Although less time consuming, finding all these can be difficult as they blend in with the environment. And some are difficult to hit. Like when EVA and Snake are riding on the motorcycle.

2) No Alerts

This one is by far easier. You have infinite saves and can restart anytime you want. Hardest place to sneak is Escaping Grozny Grad.