One thing that I've absolutely from playing a few decent Rachels, there have only really been two but I got a lot of good games in, is to make sure you stay out from under them when that take to the air, even if it puts you at range. Their drill drop thing is bad news bears, but they tend to wind up at an angle and drop straight down. So keep moving on the ground. If they miss you've got a good chance to get in and 6A them up to get your combos going. I guess that one's a bit obvious, but I've seen it hit a lot of people.
Oh and at range, they'll pop a pumpkin and shoot it straight across almost 100% of the time, so ranging can be our friend at times due to Tao's amazing ability to close the gap. When they pull it out, just 9 right over it and then do whatever you need to do to get in on them. Lots of things work depending on range. At full screen you might want to avoid drive moves because if they back up, you're screwed, but in closer than that you can usually pull a drive move and score a hit. B canceling leads to nice mixups there per usual.
Still IAD or just landing and dashing can get you inside with ease and let you open up some punishment. I personally tend to land and 66D which is what I use to open a lot of my stuff when I'm mid-range.
Hope this was helpful in some way. I know they don't cover every situation, but they're the things I try to keep in mind since most Rachels do them at some point during a match and they're great openings.