I commend you for planning ahead and seeking others input. But unintentionally/ironically you've come up with a plan which has a higher-than-average chance of ending up in a rescue situation. I'm going to flat out say that no one should make their first time on Skyline a downhill trip. Going downhill on Skyline is hellacious--in many ways it's harder than going uphill. It's definitely more dangerous. What happens if by four thousand feet your quads are shot (and they will be.) If you have not done this trail before, up or down, it's likely that by about half way down your quads will be shaking badly and no longer fully under your control. Obviously, you can't self-rescue by going uphill. What will you do then? If you stagger on down with blown quads, there's a high chance you'll fall on the many sections of slippery scree (I know, because it's happened to me.) Most of these falls aren't life-threatening, but a few are (people HAVE died on this trail of falls), and certainly broken ankles, hips, and arms, are a likely possibility. Or, even if you don't fall, you may simply be in too much pain, or too exhausted, to continue. Many times while descending Skyline, I have looked for the elevator button to get me the hell out of there, but I have never yet found it.

The problem with your alternative way to master Skyline is that your Plan B has no Plan B. Don't do it. It's way too risky.
If you want to do Skyline, follow the normal accepted plan that NeverWas and Ellen suggested, of slowly building up your mileage and gain--i.e. first hike, go up to 5k and come down. If you can't comfortably manage this, in a decent amount of time (8 hours round trip, MAX), you aren't conditioned enough for Skyline, period, and need to spend more time building up conditioning by breaking it down into shorter hikes. Once you can comfortably go up to 5k and come down in 8 hours or less, you're probably good to go for the whole trip. Yes, this plan is tedious and time-consuming, but this is the safe, accepted way to condition for Skyline.
Q: How many therapists does it take to screw in a light bulb? A: Only one, but the light bulb has to want to change ...