Hi all, looking for some advice on using these guys - it feels very difficult to safely walk them around anywhere outside your territory. You can't just point them at a location 3-4 moves away, especially as you move through AI cities etc. 

Because they are weak, they are also targeted by the AI in combat even if you try and accompany them with other units. 

Am I supposed to be micro-managing the movement of these units? Any advice anyone can give? 

I'm also not really using the stealth units very much, except when I accidentally ambush someone on my territory with a spy. Is it actually effective against the AI to have a few stealth units attempting an ambush? 

For Envoys, I'll usually send them off toward another civilization and then set them on "Auto-Explore" when they get there, the goal being that they'll mostly wander that empire's territory collecting intel for leverage against them.  If I don't have a nonagression treaty against them, though, they may attack the envoy of course.

Spies I'll micro-manage with the goal of getting them to a specific enemy tile as quickly as possible so they can exploit the tile for as long as possible.  Typically that's siphoning a specific district, but rarely I'll go for visibility on the city to see what's going on.  Note that you can Siphon District on Stategic and Luxury Resources, which temporarily grants you access to that resource.  Helpful if you're a bit shy of a strategic to make an important unit, and especially helpful if you're one shy of a resource for building a Luxury Manufactory.

Spy Master get additional bonuses against armies, which can be fairly devastating.  I might keep a Master near my own borders to throw off an approaching enemy.