It's pretty much that simple.
Obviously to keep it flowing you have to let gas escape the receiving keg as liquid enters. You could just use the keg lid PRV, or better yet a tube on a gas (gray) disconnect on the gas post. You can put that in a bucket of sanitizer just like an "airlock." When beer starts to come out the gas side, the keg is full!
To start the flow, if the fermenter is higher than the keg, gravity should do the trick -- as you say, let 'er rip. If they're on the same level, you'll need to put a pound or so of CO2 on the fermenter to keep pushing it into the keg. In any case, you need to also let gas into the fermenter as liquid leaves, just like gas has to leave the keg as liquid enters. This can be air (but that exposes you to oxygen) or find a way to apply CO2. The most elegant way some people use is to run a tube from the gas post of the keg back up to the fermenter: once gravity starts the flow it's a closed loop.
If you really want to avoid oxygen, properly purge the keg first: fill with sanitizer and push it all out with CO2.
Enjoy the fruits of your closed transfers; fresher beer longer!