I use a
6 gal Porter Cable Pancake air compressor I bought from Amazon. In fact, it's selling now for more than $20 less than what I paid last year.
I mostly got my information from this video from Keystone RV:
Winterize Your RV's Water System.
The biggest difference from the video from what I did was I had to put the plugs back on the hot water tank and the low point drains before enough air pressure built up enough to clear the water at the taps.
Also, re-watching the video, I realized that this time I used more than the max 30 psi stated in the video. In the past when I used 30 psi, I could not feel any air coming out of the taps when I opened them up. Because the adapter I bought from Camping World said max 45 psi, I used about 40 psi to blow out the pipes. This time air and water shot out just like in the video and I'm more confident that I got all the water out.