Has anyone on Active Duty been married to someone in the Reserve? How does the process work, as far as dual military?

Yes. My ex (long story) and I were both in. I was the Active Duty soldier and she was the Reserve one. During AIT in Texas (her home state) they had to start whatever 'process' some time while I was there. Luckily, Fort Drum has a Reserve unit. She got a transfer and I was simply stationed their out of AIT. I don't know what was involved, but I did see some of the paperwork since I'm on it (as her husband). That Reserve unit no longer deploys (long story), but mine did.
Being married in the military is tougher than people think. It's NOT impossible and quite doable.

My wife was commissioned into the Air Force Nursing Corp as a 2 Lt reservist. I was a Master Sergeant. The only problems were: 1. Enlisted married to an O. We had to get permission from the base commander to attend functions together in uniform 2. When we both went TDY at the same time and the kids had to be babysat for weeks.

The family care plan aspect works the same as dual active - both are liable to deploy.

Assignments are a different can of worms. The Reservist spouse is NOT active duty, so pretty much all the "dual military" stuff you see does not apply. Add to that, the assignment "systems" are completely different. Basically, the Reservist spouse will have to find a unit wherever they are happening to live at the moment - or sit some time out in the IRR. This means that the likelihood of being branch and experienced aligned goes down significantly. The good news is that there are Reserve units and/or IMA slots pretty much everywhere the Army is. Not shilling for the IMA program, but that is where I would look.

Depending on the Reservist spouse's career trajectory, there may come a time when they want to take or maintain a given assignment separate from the Active spouse. (i.e. selected for a command in location X, which is separate from the AC spouse's assignment) Keep in mind, The reserve spouse in this case in NOT eligible for separate BAH. I've seen it happen several times.