I've always driven Sebring in "momentum cars", and I know that the "high power line" is different. The line I take covers less distance and stays out of the bumpy stuff. It really sounds a lot like the line your instructor was trying to get you on, it is probably the safest line for newbs.

I always do a two-stage brake. I brake STRAIGHT and FAR LEFT at the end of the straight. I don't try to push that braking zone, usually brake at the 4th or 3rd cone. With sufficient tires, most cars can probably skip this first braking zone, but I find it to be a great confidence-builder to know that you've got brakes that early in the game!

After scrubbing off "some" speed, make your initial turn in toward the end of the wall. As Ven said, try to scrape your mirror on the wall. (you can even things up when you scrape the left mirror on the wall at turn 1) As you're driving STRAIGHT past the wall, stab the brakes again to reach proper turn in speed for the sharper second turn-in. As much as you can, you want to try to make the "perfect" turn-in so that you can hold a steady arc with minimal correction around the rest of 17, clip the exit apex at the grass near the corner worker station, and then accelerate out toward the track-out.

Faster cars will take a line where they're blowing off that first turn-in, carrying their speed deeper into the turn (trusting their brakes a lot more!) doing a single turn-in with a fairly early apex that allows them to get on the gas much sooner and gain more speed through the front straight into turn 1. It's a really ballsy line, and I think it's only necessary for those cars that have enough power to make it work. It's also harder on the suspension, because it takes you through the roughest part of 17.

There are other lines through 17. Variants of both of the above, and probably a few more that I haven't thought of yet! And if you ever get into racing, you'll want to experiment with a lot of different lines because "your line" won't always be available to take, or you'll want to try to pass there or whatever. But, for DE, just find a line that you're comfortable with and keep honing it.

Turn 16 is the one that always challenged me. In a slow car, you learn quickly that botching 16 really affects your speed in the long straight! This was driven home for me when I had a bone stock 1.6 Miata ahead of me in my mildly modded 1.8 Miata... he FLEW through 16 and I never did catch him!