I am closing the pool by myself this year and have a few questions:

1. Does it matter which pump drain plug I connect my air compressor to?

2. What is the recommended air pressure for blowing out the lines? I was thinking of using 15 PSI.

3. Do I use RV/Pool antifreeze only in the return pipes or the skimmer lines also? If so, how do I get it into the skimmer lines?

4. I read the Closing an In-Ground Pool thread and am unclear why I have to let the FC level return halfway back to normal after shocking the pool. Pool service companys usually just dump a bunch of shock in and close it up the same day. Does it matter if I don't wait for the FC level to drop on its own?

Thanks in advance for the help.

1) No, you can use any drain plug on the equipment pad as long as you can make a good connection.
2) Start low and ramp up if needed. 15 psi is a good place to start. Don't ever go above 40 psi, and if you are getting up near there then something else is going wrong.
3) Both. It should be easy to add to the skimmers, blow out the lines and then pour into the skimmer. The returns can be trickier. A angled funnel can help make the returns easier.
4) You don't have to wait, it is just a little easier on the winter cover. High FC levels can degrade the cover. The thing is that covers don't often last long enough for the effects of high FC levels to make much of a difference.

Thanks for the response Jason. I closed the pool yesterday but ran into a little trouble. The minumum setting on my air compressor regulator is about 35 PSI so that is what I used. I had trouble blowing out the skimmers and ended up using my shop vac and blowing from the skimmers to the pad. After that, I used the compressor to blow from the pad back to the skimmers to see if anything else would come out. I then dumped some antifreeze into each skimmer line and installed Gizmos. I then blew out the main drain and shut the 3-way valve with the compressor still running to create an air lock in the main drain line. I'm not sure if I positioned the 3-way valve correctly since I had some bubbling in one of the skimmers from a poorly fitting Gizmo. When creating the airlock in the main drain line, which way should the closed side of the 3-way valve be facing? Should it face the main drain line or the common outlet to the pump? I had it face the common outlet to the pump but I think that would let the poorly fitting Gizmo in the skimmer let air leak out of the main drain line. I think I may have to redo it. Also, I'm not crazy about using Gizmos. What size rubber plug should I use in the skimmers or should I use a screw type plug with an o-ring?

To seal off the drain you want the off indicator pointing at the main drain pipe. As you already guessed, pointing it at the pump allows the air to get out through the gizmo.

The correct plug size varies a little bit depending on the size of what you are sealing. 2" is #11 or #12. 1 1/2" is anywhere from #8 to #10.