There is an easier way that takes much less effort.

Set Steam to only update on launch.
Next go into your install folder and pull a shortcut of the Application/EXE to desktop.
Use that to launch the game and profit

That simple 3 step process for any game on Steam. Still have to have Steam running but it starts from the install and bypasses Steam. Been doing that for years. Used that on at least 3-4 different games.