IMO the OP did it all right. That's how it's supposed to work. It's not a marriage. Different riders are doing different things for different reasons. When they coincide, it's really fun.

IME most riders don't know the elbow flick, so before I pull off, I point to my left and down (US), then pull over to the left. I know some riders do it differently, but here the old lead rider fades back on the left while the line stays to the right, regardless of wind. This is because we ride on public roads and it's much safer this way. Of course the lead rider doesn't pull off until and unless it's clear back. A helmet mirror helps.

It's just my habit to try to run everything, so if it's a group that looks like it's going to be together for a long time, I'll run the line and suggest 3 minute pulls, which is about a mile as a previous poster said. If I'm comfortable, 3 minutes is my usual. If others are weaker, I'll pull longer. If I pull off and the pace drops too much, I'll come up and take back the lead, just like the draftee did when the OP went to the hoods. I think it's really cool when one can team up with another rider even for a little bit. We talk with our bikes. There's a language which one gets to know. I say, you don't really know someone until you've ridden with them.

If it's just a casual encounter, I'll pull over, see what happens. If they don't pull through, I'll take it back, no problem.

If you're trying to hold a line together because you're faster with a line, duh, when you come to and over the top of a rise, don't accelerate like you would solo, rather back off on the pedals a hair because the rider behind you isn't feeling it getting easier as quickly as you are.

Oh, right, etiquette. When I get on someone's wheel, I call out "Wheel."