How to make a Prokill?
Well that's easy.
All depends of your patience and movements.
The first thing is, to choose location from where u have clear shoots.
Then you need to do in every location (Spot) only 5 kills.
That you repeating from every spots 4 times. It means that you kill from 4 spots 5 enemies then u will get 20 kills and that is actually Prokill.
For example you have 4 spots (A, B, C and D).
You making 5 kills from spot A and moving to spot B then making 5 kills more than that's will be 10 Kills (Stormkill). Then you moving from spot B to spot C and making new 5 kill then you will have 15 Kills. And the last movement is from spot C to spot D and you making 5 more kills until u get 20 Kills (Prokill).
But remember:
Every time before you decide to switch your position from one spot to another one be sure that there is no have any enemies around your current spot, you won't to be death during your movements from one spot to another (From behind, from your back). Always check is everything clear that u can safetly changed your position, then move.