Do you wish you could play versus, but without all the pressure of playing with other people who want to win? Do you just enjoy running around as the Special Infected and beating up on helpless Survivor Bots? Then I have just the thing for you!
Rayman's Mutation Mod!http://steamcommunity.com/sharedfiles/filedetails/?id=121070254
Behold! Simply subscribe to his mod, and then go to Custom Mutations, Versus Mutations, and then Versus Coop.
Then, simply start a game. Play as the Special Infected. The bots will work their way through the map by themselves (just warning you, they rush). With only one player, your spawn timer will be like 5 seconds. After you crush the bots, once the new map starts....just switch teams back to the Infected and kill the bots again. They're just bots, they won't care about your team switching. In fact, you can switch teams as many times as you want, which sometimes you need to do, e.g. cola event in Dead Center.
You can even play with friends! Everyone can play on the Infected and slaughter the bots together! And there's no pressure to make sure you pull off the death charge etc.
And because you're just playing against bots....who cares if you cheat? Spawn yourself as the Infected of your choice so you can get more practice. Work on your tank rock curve, practice 25 point pounces, death chargers, etc.