Welcome, sir.
Clippers are designed so that they will not hurt your skin, so do not worry about using them without the guard. And yes, it is very possible to get an even length all over your head.
As for looking Sly smooth after the clippers, well, that depends upon what you think is too smooth. No guard is going to get you almost to a shaved look. If that is too bald for you, I would suggest you start off using the guards on the clippers working your way shorter and shorter until you get the length you like.
Remember that if you do go too short, that perfect hair will grow back to the length you liked within a couple of weeks.