Is it allowed to use the dry conn inside the AC disconnect box? I figure it could only help.
What's a DryConn?

I figure it could only help.
Why? When I did the sprinkler connection. I just wiped the grease down and put on a new one

I am installing a surge projector on the AC. I am tempted to just double the wire under the screw. Otherwise I will.need to use a wire nut and extra wire.
I used some of those on my outdoor light and they were not exactly what I expected. They just didn't grip the wire ends enough to twist them properly. I ended up taking one back off creating a mess everywhere. I used my Ideal wire nuts on the next connection.