Rob,
Good decision. I only recently began transitioning to cloth diapers for night, so I understand what you are going through.
Before you buy, the most important consideration is the size of the flat diaper. Do not buy the smallest size that the tables on the site say should fit you - you will find it almost impossible to pin the wings. Initially I made the mistake of buying a flat diaper too small to properly fold. Also, there was not enough material left at the side of the legs where leaks occur for side-sleepers.
Choose your fabric. Gauze material absorbs pee the fastest. Birdseye is next, and a little more durable. Flannel is very durable but very, very slow to dry.
Do note that flats often are available in different layers of fabric, such as 2, 4, or 6 layers. You can choose to fine-tune the absorbency by choosing the layers. Remember, that as you are not buying prefolds, you need to have extra layers for absorbency.
Now I buy the 44" square gauze purity flats from Adult Cloth Diaper. I also buy the ACD prefolds. That leaves me the option of using a flat diaper inside a pre-fold when I need extra absorption, such as after that second beer.
Just lay the two flats on top of each other. Fold to your desired pattern. Please note that you only need to pin the outer diaper, not both together.
Don't forget to buy pins. They do not need to be giant diaper pins. The oversize pins actually are much more difficult to push through the fabric.
You must wear plastic pants over cloth diapers. Cloth will wick - that is its beauty. However, that means that if part of the wet diaper is not covered by the plastic pants, pee can wick onto the bedding. Some plastic pants intended for disposables will not fit over cloth diapers.
Good luck and keep us posted on your progress.
--John
It makes me feel cared for and appreciated