Yay, another solution -- I did a video and wrote up the technique though, hope it helps someone.
This shows how to get A LOT of Perfect Drafts. This is specifically for the following achievement:
Dirty Air 15G - Get 100 Perfect Draft Scores
Following this guide will allow you to get them quickly, in one showcase race: Daytona (30 laps). You will also unlock the In The Draft Platinum NASCAR badge in the process (shown in video @ 0:24), which you can equip to also get the following achievement:
FYI, completing this showcase alone is also enough to net you the following achievement:
Technique:
0. Choose NASCAR Showcases and pick Daytona, you can verify it's the right one because it will be 30 laps
1. Set Drivatar Difficulty to Average or Above Average -- anything below this will make it difficult to keep a car in front of you
2. Work your way toward the top, this can take a few laps. Don't worry, there's plenty of laps even if it takes you 5+ laps.
3. Get behind the 1st car and feather the accelerator. The main thing is to be squarely behind the 1st car, not too close, not too far, as shown in the video. It's not too hard, after a bit of practice in a few laps you will even be able to get perfect drafts while cornering. Distance should be 2-3 carlengths back, reference video for example.
4. You should aim to get at least 10 drafts per lap. Don't worry if this is not happening in the beginning, it will take a few laps of practice once it's just you and the #1 car in front of you, but at 10+ Perfect Drafts per lap, you only need 10 laps to get this.
5. Once the "In The Draft" Platinum badge pops, you're done. The "Dirty Air" achievement doesn't pop until you finish the race, but you can go ahead and take the #1 position and just race to the end in 1st place.