Here is a scheme very similar to one I used to get a 21:20 Filthy Fifty. I will use this one to try to break the 20 minute mark next time it comes up. It would helpful to have a coach to keep you on the mark, but you could do this by yourself with a stopwatch with a big display. The key to a quick time on this workout, in my experience, is to arrive at the double-unders without being so winded that they are nearly impossible. If you find yourself unable to do them, sit down and wait one minute. Recovering is more efficeint than trying and failing over and over and over.

25 Box Jumps: 1:00
rest: :20
25 Box Jumps 1:00
50 Jumping Pull-Ups: 1:00
50 Kettlebell Swings: 1:20
50 Walking lunge: 1:20
50 Knees-To-Elbows: 3:00
50 Push-Press: 1:00
50 Back Extensions: 1:20
20 wall-ball: 1:00
Rest :20
20 Wall-ball 1:00
Rest: :20
10 Wall-Ball :30
Rest: :15
25 Burpees: 1:45
Rest: :15
25 Burpees: 1:45
Rest: :10
25 Double-Unders: :30
Rest: :15
25 Double-Unders: 30

Time: 19:55