Playing in the higher ranks of Counter-Strike: Global Offensive requires much more than just quick reflexes and good aiming. Having a strategic advantage when entering an aim duel greatly increases the chances for success.
Using grenades to gain such an advantage can be trained on an empty map to find out how to throw them in the perfect way. To have a lot of time and infinite smokes and other grenades makes training and perfecting these things a lot less painful.
To make use of such a config simply create a new file called train.cfg in the cfg folder of your Counter-Strike installation and paste the values below into that file. Create a new game with bots and when in-game type exec train.cfg to load the config.
// Training Config
bind "MOUSE3" "noclip"