Never heard any mention of this so here it is:
Just grab the enemy near the edge of the map and use snakes down throw(the distance where he end up is where you see the animation change), as soon as you let the victim go plant the C4, if it work you will see the C4 somewhere on the enemy, after that run like hell because just touching the enemy will transfer the c4 to you, attacks won't transfer it but it can drop it for some reason.
Just grab the enemy near the edge of the map and use snakes down throw(the distance where he end up is where you see the animation change), as soon as you let the victim go plant the C4, if it work you will see the C4 somewhere on the enemy, after that run like hell because just touching the enemy will transfer the c4 to you, attacks won't transfer it but it can drop it for some reason.