This is how you speed crouch in the game. This allows you to get the full speed benefit of sprint from the standing position, and also have the noise and detection of crouch. All you need is an "Elk Caller". You will remain in crouch untill you ADS, press CTRL again, use elk caller etc...

Use the "Elk Caller" then hit "CTRL" to crouch. Wait one second for the animation to get bugged. (I believe that is what's happening) hold the "SHIFT" key for sprint, Press "W" to walk forward and proceed to hit "SPACEBAR" to raise. This won't actually raise you but you will get the speed benefits of standing position.

That is -> (1. Use Elk caller) (2. go crouch) wait 0.5 seconds (3. Hold Shift) (4. Walk Forward) (5. Press Spacebar)

Now you can run up to wildlife and blast them with your shotgun to further increase your skill.

I couldn't find a similar guide elsewhere.
I found this exploit by chance... Enjoy!

It has come to my attention that there is an alternate method which is more efficient than the last.
I felt it would be far to lazy of me if I did not include it in the guide. Enjoy and thanks to Luraman.

Luraman ʸᵃʸ 3 Oct @ 11:42pm
@Crash
I've found a consistent alternate method with no caller required!
First aim-down-sight with anything while standing.
Next, quickly input crouch, drop aim, stand. (Ctrl, RMB, Space for me)

This is much faster and also you can re-execute it everytime you're finished aiming to reapply it.