Training Popflashes alone is barely possible and extremely hard to do. Even with two players it's tiresome and takes quite some time to explain each other how exactly to throw it, switch positions and observe the effects.

I wrote a script that makes the process much easier: You just throw the flash once, move to wherever you want to see it from, throw another and it will come flying the same way the first one flew.

Here's a video of it in action:

This will not get you VAC-Banned or anything like that, it is a regular vScript, as found in custom maps.

1. Download the script from {HIVATKOZÁS TÖRÖLVE}medifire (or get the source from github[github.com])
   
2. Put the file into SteamApps\common\Counter-Strike Global Offensive\csgo\scripts\vscripts
   
3. bind script nadeSavePos() to a key

For example:

1. Start a new match without bots (or play on your server with the script installed), casual or comp
   
2. enter sv_infinite_ammo 1 into the console to have infinte grenades
   
3. enter script_execute nadetraining and script nadeSetup() to enable the script
   
4. buy grenades
   
5. Press the "nadeSavePos" button (, in my example)
   
6. Throw the grenade you want to check out from different angles
   
7. Now, go to wherever you want to view it from and throw another. Observe the explosion/flash
   
8. Repeat 7, go to 5 for another nade.

I of course appreciate donations and ratings, if this becomes popular I might be able to add more features and write more scripts.

Have fun & Good Luck